Where does “leuco-” come from?

leuco- (Spanish) comes from Ancient Greek λευκός, from Proto-Hellenic *leukós.

Ancestry of “leuco-”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	λευκός	bright, shining, gleaming; light in color; white;...
2	Proto-Hellenic	*leukós	—

leuco- — Etymology, Origin & Word History | Etymology Explorer