Light consists of waves of energy of different lengths. When light is refracted it is split into different wave lengths which appear as different colours – hence the rainbow. When light strikes an object, certain wave lengths are absorbed and others are reflected. Colour perceived (eg. skin colour) depends upon the wave lengths reflected.
Those with the divine nature (the angels and Jesus after his resurrection) can both absorb all light waves (become invisible) or radiate the full spectrum of light.
Luke 24:31 And their eyes were opened, and they knew him; and he vanished out of their sight.
Acts 26:13 At midday, O king, I saw in the way a light from heaven, above the brightness of the sun, shining round about me and them which journeyed with me.
God can therefore both absorb light and emanate light at will.It follows that God has no generic colour but can appear any colour he wishes. In our mortal state we cannot see God anyway.
1 John 1:5 This then is the message which we have heard of him, and declare unto you, that God is light, and in him is no darkness at all.
1 Timothy 6:16 Who only hath immortality, dwelling in the light which no man can approach unto; whom no man hath seen, nor can see: to whom be honour and power everlasting. Amen.
All skin colours are descendants of Adam. All are condemned to death unless they believe and obey the gospel preached by Jesus Christ. In Christ, skin colour is irrelevant.
Colossians 3:11 Where there is neither Greek nor Jew, circumcision nor uncircumcision, Barbarian, Scythian, bond nor free: but Christ is all, and in all.
I hope you find this helpful.