Thanks for all the work and feedback on this.
Current UI is very nice as is. I do appreciate that you are considering adding option for color icons as well. I have enabled it, and I like it so far.
I don't know what is easier and preferred option for both you and most users. Color icons make things visually a bit easier/faster - that is just me. I do like monochrome UI a lot, and it is a step forward. It does get some getting used to at first. I like the fact that you did not make UI too dark (Affinity Photo/Pixelmator).
If color icons require too many changes, would you consider adding some color to toolbar icon when a tool is selected? Keep current icons, but change to color icon/or tweaked version of it, when selected. Reverse of what it currently does when color icons are enabled. Monochrome Pencil/Eraser icons are what I am thinking about, and what you have done on color version of Paint/Flood Fill tools. A sublte touch of color.
I hope I have not confused you with feedback. In short:
- Keep on working new set of icons and possibly make it user selectable so everyone's happy.
- Tweak current set with a (subtle) touch of color (like current Paint/Eraser tool icons)
- Keep default set but consider only tweaking selected state icons - either full color or some color to distinguish it.
This is not a request for v5 UI. Marley a suggestion of what you might improve. Maybe you could try experimenting by making changes to 4 icons/tools, and see what is visually nicer/fits better. It's, of course, up to you and feedback you get from others.