It was interesting discussion if it is ok to calculate the ease of getting red using percent of reds. But even it is not ok I was determinated to know what part every color takes if we exclude users who took part in few contest. About an half of users leaves CF before their 5th contest. I have not any stats about robots though)
So for human stats looks so:

If minimal number of contests is 5:

You can try other parameters on interactive dashboard. Hover the mouse over color areas to see more details.
Script code is here.

The current color scheme was introduced in October 2015 and updated in May 2018. One of the reasons was that getting red had become “much easier”. Is it true that at some period it could be easier? Certainly it is not my practical concern, but I still wonder ) So how can we measure this ease to get red?
It looks like it will be several iterations but for base line I would like to know what percent of CF users are red. I ran the script and found number of active users of every colors and every title for the end of 2018, 2019, 2020 and 2021. I mean number of users who were active in the corresponding period. Feel free to download .csv files and play with them, but it is really convenient to do it in Tableau – this is the dashboard with selective options. Its left part represents percent distribution by colors, the right one is by titles. You can select options for left and right charts independently and for example discover that you had to be in top 0,67% — 0,65% — 0,69% — 0,67% to be red and in top 6,61% — 6,31%-5,91%-8,47% of reds to be legendary grandmaster. Is it getting easier to become a legend? )

I hope I don't steal words from future MikeMirzayanov's blog about 2021))
There were 142 contests (rated and unrated) in 2021. How many users participated in every of them?
The smallest number of participants is 31. It is VK Cup 2021 - Final (Engine). The greatest number is 19332 at Codeforces Round 697 (Div. 3). This numbers are got by API and include all official participants. But not all of participants were marked as “trusted participants” so there are usually less users shown in the contest final standings. Stats lovers can get more info from the interactive dashboard. Hover the mouse over columns to show info.

On January 4th I ran my script to download user profiles and sum how many users registered in different years had already logged to CF in 2022. Today is 9th, but I have some problem with API and could not update my data. So if somebody had been online already but was not included in statistics and doesn't like this fact — feel free to write DM to me or add a comment and I'll fix the issue :-)
Pay attention that bar chats use different scales.

MikeMirzayanov in this blog asked a question about fighting against meaningless blogs, so I am in hurry to post this picture before rules become strict :-)

I am very glad to introduce my guests from Deltix:
Aliaksandr sdryapko Drapko, the Head of Technology of CryptoCortex product and
Vladislav Vladik Vishnevsky, the coordinator of all competitive programming activities by Deltix and the key developer of MarketMaker product.
I am proud to be their compatriot, so let me start with some belorussian words of greetings
- Прывiтанне, Аляксандр і Уладзіслаў!
- Прывiтанне, Наталля!

- Deltix is the sponsor of the Belarus National School Olympiad in Informatics. Last spring you represented Deltix at the National Final award ceremony. The award ceremony was very touching for the winners. But what about you? How did you feel presenting them prizes? What were you thinking about at this moment?

Aliaksandr sdryapko awarded a winner at Belarus National Final, 2021
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Every time when a dispute arises if the pretest were just bad or the worst in the history, I wondered what is a typical part of submissions failed on full tests. I ran my script to calculate this value for Codeforces rounds. The value is based on 895 Div.1 and Div.2 rounds which were held since 2012. The histogram for 4846 tasks is shown below

If you do not participate in rated rounds for 6 months you get status “Inactive”. Does it mean you are really inactive compared to others? What is a typical interval for users between their contests?
I ran my script on Oct 31 2021. It collected information about intervals between rounds for all users who have at least one interval, that means who has taken part in at least two rounds. It discovered 283412 appropriated users and counted 4552393 intervals.

95% of intervals are shorter than 113 days.
Percentage of intervals shorter than 183 days is 97,09%.
Mean value is 27,5 days, mediane is 7 days.

Let’s look at the distribution of duration for intervals less or equal to 183.

So it is totally ok to mark users as inactive after a six-month absence. But I was just curious to find out somebody who came back after being inactive for a long time. What do you say about 11 years absence?
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I know we can filter contest results to show only friends. But MikeMirzayanov has 6554 friends and as far as I know does not participate into contests. So does it mean something special to have a lot of friends on CF?

Country and city in Codeforces user profiles are often not a the place of the residence but a state of mind. I am sure those 197 users who selected Antarctica as their country feel that their surrounding is cold. Or cool ) The map below shows data from user profiles which have both country and city. So only 16 of all antarctic profiles were taken into consideration, because other have empty city field.
On 27 June 2021 there were 351898 users in the rating list. 88752 profiles contained both country and city. There were 4162 unique values of City field for 180 unique values for Country field. The size of circle is proportional to user number and different colors are used to divide cities on groups with the following numbers of users: <20, 20-99, 100 -249, 250-999, >1000.
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SimilarWeb is a platform for web analytics. It allows you to collect data for any sites even when you are not their owner. It is an expensive tool but some features are available for free for the start period. When I tested how it worked naturally I chose 'Codeforces.com' for my exercises:-)

The very first picture surprised me.

I ran my code on 28 May 2021. There were 345553 users in rating list. 87427 of them set field City in their profiles. There are 4009 unique values. Certainly some profiles might have fake values but anyway it is interesting to look at all these points on the map. Cities are marked by circle if there is at least one Codeforces user profile with this city name.

Please meet my today's guest Anatoly ruban, PhD in Physics and Mathematics, who yesterday participated in his 700th contest on Codeforces.

The plot shows correlation between number of contests and max rating of a user for all (included inactive) users.
Changing in calculating rate for newcomers are easily to remark.
Although there is no correlation between number of contests and max rating I am mesmerized by people who have great number of contests. The diagram shows that their results are really outstanding.

At the beginning of March 2021 there were 324234 user profiles in the ranking list on Codeforces (my code on GitHub). About a quarter of them (81918 users) took part only in 1 contest.

Now (13 March 2021) there are 6786 problems on Codeforces (my code on GitHub). 142 of them have no rating. What is problem complexity distribution for 6646 problems which have rating?

What was the most popular day of week for contests?

Arpa's interview:

-Salam AmirReza
-Salam Natalia

-Do you remember becoming red?
-Yes, exactly one year ago, for the first time, I touched red just with 2405 :))

As I wrote before only 1622 profiles on Codeforces have in their history a rating more than 2400 (February 2021). How many days are between the contest where a user became red and his first contests?

The most popular question on Codeforces must be "How to become red".
I've just (February 2021) ran a script and discovered that the current number of Codeforces profiles is 323553. Only 1622 profiles have in their history a rating more than 2400.