I really like using the triangle in Gimp and Inkscape. Could we add it in Synfig?
Yes, we can try to include it in next releases. It was proposed as a patch some time ago but we decide to not implement it because it doesn’t allow to use decimal numbers for the RGBA channels selection.
Color wheel?! I dig this idea!
We could improvise on the RGBA thing. How about put an Alpha slider just below it, like Inkscape does?