Right, custom materials don’t work too well. Custom material is on my list of issues to fix. However, I’d like users to move to the Physically Based and canned materials (Plastic, Paint, Glass, Metal, Gem), since those are more in line with the capabilities of the underlaying render engine.
You can copy the color to the clipboard (right-click on color, copy color), then change the material type from Custom to Plastic. Paste the color you copied as the plastic color. Ensure transparency is set high, 95-100%.
For Rhino Render / Raytraced I would bump the value of the color to 100 and saturation down to 3 otherwise it will look quite dark blue.
