Improve colors' appearance in the editor's print_rich() output

[Calinou]

This matches most terminals' behavior which don't use "pure" ANSI colors anymore, but use modern color palettes instead. This improves readability and allows the colors to adapt to a light-theme editor.

Testing project: test_richtextlabel_color_alias.zip

Preview

How it looks like in VS Code's integrated terminal for comparison (using the default Dark Modern theme):

[Riteo]

I approve the idea but IMO I feel like some colors, especially red and green, are a bit washed out. Could they be saturated a little bit more? Look at VSCode in comparison.

[Calinou]

I approve the idea but IMO I feel like some colors, especially red and green, are a bit washed out. Could they be saturated a little bit more? Look at VSCode in comparison.

I've reused the editor's error (red), warning (yellow) and success (green) colors. The blue color is based on the default accent color (but it does not change if you customize the accent color). I guess we could make those colors more saturated to match the increased icon saturation in 4.0.

[Riteo]

@Calinou

I've reused the editor's error (red), warning (yellow) and success (green) colors. The blue color is based on the default accent color (but it does not change if you customize the accent color).

Oh, I see, so this is a more general problem. I'd saturate everything honestly. The question then becomes: do we saturate everything in one PR or in two parts (default and print_rich)?

[Calinou]

The question then becomes: do we saturate everything in one PR or in two parts (default and print_rich)?

These can be done independently, so I think it's best to do that in a separate PR. We may want to further tweak the light theme colors for those as well.

[Riteo]

@Calinou all right.

[Calinou]

Rebased and tested again, it works as expected. This PR now incorporates @dalexeev's BBCode replacement method, so I added them as a co-author.