all the characters I create turn black, how can I solve this?
That comes from the new shader. Does this happen every time? Can you check the version of DirectX you're using? Game Maker requires DirectX11 or higher for the shaders to work properly.
If it doesn't fix it, I'll try to make a compatibility option that doesn't use shaders.
Is anyone experiencing the same kind of issue?
What about your graphic card drivers? Are they up to date?
I will try to tweak the shader a little in the next version to see if it helps, since it seems to be working on at least a couple colors it might be that the color selection is a bit too strict for some computers.
I have added the compatibility option to my backlog, I'm not sure if it'll be ready for the next version and I will most probably have to make some features unavailable when using this option, but it should at least make the game playable.