timo
timo What exactly do those colors represent? The amount of entries per day? The amount of tags? What if people don't add any colored tags or multiple, different colored tags per day?
The colors represent the tags. The main idea would be to define tags and assign a color to each, so basically the color becomes representative of the tag. And then, when you assign tags to an entry, you should be able to see the colors of the tags in calendar view. For example, if you assign 3 tags (1 red, 1 green and 1 blue) to an entry, then you should see 3 (1 red, 1 green, 1 blue) bars/squares/whatever (like in the Quillio example). That way you have the entries visually classified.
For instance, maybe you have the blue colored tag for a very stressful day, or the red one for when you failed to control an addiction, or orange for parties, etc. And being able to see all that in the calendar view at a quick glance would be a huge feature IMO. In fact, in this Quillio app image I posted, where there is an entry with 3 colors, I know it has 3 tags and which ones they are, just because of their color, without having to look at the name of the tag, and I can have an idea of what happened that day.

I understand not everyone will want to organize them like that, but it would give us the freedom to do so if we want to. And maybe more people would gladly do it if they saw that feature.
That said, it wouldn't be exactly the same as adding a color to each entry, because that would limit us to only 1 color per entry, plus we would have to remember what each color means. Whereas with the tags, we just have to assign the tags we want, and each entry can have multiple.
Of course, different tags can have the same color, or not have any color assigned at all. Well, in the first case, it's no problem: just show 2 props of the same color. But well, if the user wants to make tag colors be like an ID for the tag itself, then they are free to use different colors, especially with the great feature of the color hue (unlike in Quillio where you are forced to select from 20 colors 🙂). So the user itself can counteract it in that sense.
And if there are tags with no colors, well, idk; maybe dont show them, or show them unfilled, or show them with the default color like how the entry with no image is filled.