The color adjustment filter has a "channel" selector where the default option is "RGBA," but while this option is selected the alpha channel isn't processed by the filter. It should say "RGB" instead.
Hi Noel, thanks for your report To be hyper-specific: this is about the "Color Adjustment curves" filter. I cannot personally attest to which is more correct (RGB vs RGBA), but it sure does seem like the alpha channel is unaffected and that RGB is a more accurate label. Should be an easy fix in that case.
A possibly relevant merge request was started @ https://invent.kde.org/graphics/krita/-/merge_requests/2573
Git commit 231d117c5a2f843db9393d555f7be3381767cb21 by Wolthera van Hövell tot Westerflier. Committed on 17/12/2025 at 10:34. Pushed by woltherav into branch 'master'. Make the all-colors channel in the adjustment filter not contain "A". We don't seem to have a generic function to only get the names of the color channels, or even a way to find canonical short names for color channels, so hardcoding them for now makes the most sense. M +15 -2 plugins/filters/colorsfilters/virtual_channel_info.cpp https://invent.kde.org/graphics/krita/-/commit/231d117c5a2f843db9393d555f7be3381767cb21