The Masters and Layers panel is primarily useful for variable fonts, so you can safely close it if you’re not working with variable fonts.
Regarding creating color glyphs, there are a couple of methods that turn your glyph into a color glyph.
The recommended way:
Right-click within the Glyph Panel after importing your glyph outline. Select “Colorize” from the context menu. This action will add the glyph as a color glyph member and automatically set the color mode to COLR.
Alternative way:
Switch to COLR mode using the toolbar. Open the Glyph Members palette. Manually add your glyph to create the desired color layer.
Most of this is covered in this part of the user manual:
Let me know if something is unclear in the manual, so we can improve it!
Hope this helps! If you have any more questions or need further assistance, feel free to ask.