7.3.3 Rainbow

From [pov:6.9.5]:

RAINBOW:
    rainbow { [RAINBOW_IDENTIFIER] [RAINBOW_ITEMS...] }
RAINBOW_ITEM:
    direction <Dir> | angle Angle | width Width |
    distance Distance | COLOR_MAP | jitter Jitter | up <Up> |
    arc_angle Arc_Angle | falloff_angle Falloff_Angle

Rainbow default values:

arc_angle     : 180.0
falloff_angle : 180.0
jitter        : 0.0
up            : y