What does callainus mean in Latin?

callainus, a adjective, means “turquoise, green-blue”.

How do you pronounce callainus?

In classical Latin, [kalˈla.ɪ.nʊs]; in ecclesiastical (church) Latin, [kalˈlaː.i.nus].

adjectivefirst/second-declension adjective

callainus (feminine callaina, neuter callainum)

Classical[kalˈla.ɪ.nʊs]Ecclesiastical[kalˈlaː.i.nus]

singular
form	masculine	feminine	neuter
nominative	callainus	callaina	callainum
genitive	callainī	callainae	callainī
dative	callainō	callainae	callainō
accusative	callainum	callainam	callainum
ablative	callainō	callainā	callainō
vocative	callaine	callaina	callainum

plural
form	masculine	feminine	neuter
nominative	callainī	callainae	callaina
genitive	callainōrum	callainārum	callainōrum
dative	callainīs	callainīs	callainīs
accusative	callainōs	callainās	callaina
ablative	callainīs	callainīs	callainīs
vocative	callainī	callainae	callaina

Borrowed from Ancient Greek καλλαΐνος (kallaḯnos). By surface analysis, callais + -nus.