Adjust handle colors on the fly
Adobe doesn't take colorblindness into account when coloring the handles in Illustrator. I'm not talking about layer colors -- I don't care one whit about layer colors. I'm talking about the associated colors of the handles for the layer, which is the same color as the layer. You can keep layers colors multivariant if you wish, but when working within a document, I simply cannot see the handles when the layer color is against a color in the document that I cannot distinguish between. I've tried resizing the handles, but that does not always make a difference. My only workaround is to "throw layers away" until I can find one that is properly distinguishable.
@Egor: inverting the color beneath the highlighted edges/handles is a very interesting idea. I'm not sure why I didn't think of that before, I use that cursor option in Windows.
A user should be able to use predefined colors for new artboards, that is correct. I know people who prefer black, who hates yellow, who always stick to default blues, who would like to have inverse edges, relative to the artwork beneath (!).
Having a blue art in a blue colored layer forces me to switch it way to much :(
Glad you found my suggestions helpful. I'm going to vote for this anyway because I think some sort of accessibility features for colorblind folks would be a welcome addition one way or another.
Andre Hinds commented
Lance deserves a big vote of thanks. That’s precisely the kind of advice I was looking for. I love Illustrator, but sometimes you have to be a superuser with it, am I’m not that.
In addition to changing the handle size, have you tried changing the handles to the white/gray fill instead of the solid color? In Preferences under Selection & Anchor Display > Handle Style. Unfortunately that only changes the handles not the anchors.
Something else that might help: Have you tried selecting a pre-existing layer color from the built in list, or creating a custom one? Double-click in the blank space to the right of the layer name (or use the layers pallet menu > options for "layerName". It'll give you a small dialog with options including the color list. At the top of that drop down list is "Custom..." which lets you choose any color you would like. That'll set the layer's color and subsequently the selected object's highlighted edges, handles, anchors etc. to something that would be easier for you to see.
I use this pretty often when the default selected by illustrator is a poor contrast to the art I'm working on. I can usually find something in the list that works but it sounds like you'd get more use out of choosing custom colors.