Most tubes use the dye item for colors, but the request tube uses the painter item in the color picker. I think it would look better if all used the painter item, or all used the dye item. I think the painter item like it is used in the request tube is the better way to go because it has the empty painter to display that nothing is picked, and always having something displayed in a color picker field would make it easier to see what the input is about in the first place.

And if I open the gui of a Tester/Checker, I have to actually click into the slot to see what it is about, using the painter here also would make that easier. If it is a setter or getter is pretty obvious normally, if I open a color filter tube, I would not expect that it changes anything, and also, setters use buttons while getters use slots, as far as I could see, so the difference would still be there

honestly i get where you come from, but is like really picky at this point...
So unlikely to happen.
Out of the 3 opened issues, this is the only one i would consider to say no to.

Actually it is unified already.
Emitters that "Set" colors use the Painter.
While Testers/Checkers use the Dyes.

That way you can see if it is a setter or a getter.