Differentiate colors for diff background, highlight, and margin

[manvithn]

Kitty's default diff color scheme uses different shades for the margins and highlights of kitty diff. This adds similar color variation for the catppuccin diff color schemes.

[unseen-ninja]

I really like this change; looking at this I'd even suggest to increase the difference just ever so slightly more – just by 5%, max. 10%. I'd like to hear your and the other maintainerss input on that. c:

[manvithn]

Let me write the intensity of the colors like this: background-highlight-margin

This is mocha at 25-45-35 (current PR):

This is mocha at 30-50-40:

I find the first a bit more readable, especially the white-text-on-green-background at a lower screen brightness, but the background does feel a bit anemic compared to the second.

And finally this is 30-45-40:

This addresses the two concerns above, but the contrast between the background and highlight is lacking. I don't really have a strong preference but I think we should stick to either the first or second, I prefer the highlight to stand out a bit more. I also don't want to increase by more than 5% because readability starts to suffer at that point.

[unseen-ninja]

Thank you very much for this – but oof, that's a lot tougher than I thought it would be. Personally I like the second example the most, tho readability is worse with compared to the first one. But I'd want to argue that it still makes the most sense in terms of overall clarity.

[manvithn]

Alright I updated the themes to 30-50-40. The richer background looks quite nice.

[unseen-ninja]

I'll just take the libery of merging this. Thank you very much!