2 colors on glyph for no reason?

Glyphs
1

For some reason unknown to me, one of my f
2 color glyph
glyphs in only one of my masters has 2 color designation.

2

Hold down the Option key when selecting a second color, deleting or changing one.

3

The second color is on the layer. With the option key your can change it.

4

Thanks! I never knew a 2nd color was even possible.