Hi,
By default, the color scheme matches that of mumax3. (1,0,0) is red, (-1,0,0) is blue, (0,1,0) green, (0,-1,0) purple, (0,0,1) white, and (0,0,-1) black. Directions that aren't along one of those axes will be a blend of the relevant colors (for instance (1,1,0) will be orange, between red and green). This picture from the examples page may help:

This is just a 2-D slice from the mumax GUI, but the same principle will apply in 3-D
Best,
Josh L.