Multiracial casting is fine. Of course, who is available for the roles will determine a lot, but such casting needs to be done sensitively.
Mundo the Fool would be great played by an African-American or other dark-skinned actor. He aims to seduce Eldora the princess, who could be Asian, white, or light-skinned, which would set a further challenge to their improbable falling-in-love.
Other multiracial casting needs to be sensitive to how the conflicts between characters may be perceived. Mundo the Fool, for example, rejects the Emperor's bastard daughter Espi to be his wife. A light-skinned Mundo, however, should not be rejecting a dark-skinned Espi.
This musical calls for heavily stylized makeup to complement the gaudy costumes. With multiracial casting, the challenge is to make all shades of skin color equally stylized and visible to the audience. Light skins need dark-colored makeup; dark skins need light-colored makeup. Medium skins can go both ways.
Each character page on this website gives a few images to inspire stylized makeup for each character. Below we give a few more images to inspire stylized makeup options for darker skins.