Ultramarine Blue plots cooler and bluer than the more saturated French Ultramarine. Temperature aside, both blues have equal permanence, lightfastness and semi-transparency.
Ultramarine Blue is slightly less granular in concentrated washes. For less saturation, sedimentation and cost, use Ultramarine Blue straight, for vibrant crayon-like color or mixed with a cool red for dark, effective neutrals.
Complimentary color is:
Aureolin (Cobalt Yellow)