Hi Ramon, thank you a lot! Sorry for not replying you sooner, I was offline the past days.
About the different icon colours, this is a bug, icons colours are automatically handled by Krita based on how light/dark the theme is, some things don’t change when you select another theme, then you have to restart Krita for it to change.
About the low contrast in isolated layers: I never use it, so I didn’t knew about this issue. I tested and this happens in the neutral theme that comes with Krita by default, then I guess it is just how Krita behaves, apparently it always makes the text on this mode to be a mid-grey no matter what theme you are using (maybe a bug report is a good idea, but I don’t know if it is worth it).
Since you pointed out about saturation in the green theme, I think the accent colours of neutral themes may benefit from being less saturated/less brighter (since it’s kind of the point for neutral themes to be as neutral as possible). To finish, I don’t think there is a way to make the transparency of the selected brush less transparent, probably handled by Krita as well.
That said, thank you for your feedback Ramon, I’ll take notes to the next update!