Problem: Now Oxygen Builder supports using CSS variables, but it does not show color preview. Workaround Solution: Import all stylesheets inside Editor. Potential risk: CSS collison with Editor, breaking few things. If collision happens you can use Quick Fix to remove it from Editor. Potential better solution in future: Marking stylesheet with color variables with some special comment */##COLOR##/* which could make parsing easy. So if stylesheet is starting with that comment it will be pulled inside Editor for eg.