To help you preview the eyes in blender:
On your 2nd image from the first post with the black material on the eye mesh, go to materials, set blend mode to alpha blend (see the bottom right corner of the image I posted earlier). The black area should become transparent.
For the bright purple, the pointer for the skin texture image lost track of the file.
Use either image editor or uv editor. Select Image/Replace… then apply the skin texture. Chances are, simply Reload (Alt+R) won’t work since the pointer looks like it failed, e.g. if the texture file or blender file are moved to another folder.
I’m still lost on setting up the eye color to change.
For the skin I made, the AvatarMaskEyes_MAT doesn’t seem to work for eye color change in neither build editor nor test server. My skin is basically ready, I’ve already updated the eye artwork for my final design. Mapping the iris to the eye color palette is the missing piece to the puzzle.