From Longman Dictionary of Contemporary Englishultramarineul‧tra‧ma‧rine /ˌʌltrəməˈriːn◂/ noun [uncountable] CCa very bright blue colour —ultramarine adjective
Examples from the Corpus
ultramarine• The mass effect was of a light but most brilliant ultramarine.• He was gliding softly through the water towards the deep ultramarine stain the sloop made in the brimming blackness all around.Origin ultramarine (1500-1600) Medieval Latin ultramarinus “coming from beyond the sea”; because the substance it was made from was originally brought from Asia 