'pastel-colored' is a compound formed in English from 'pastel' and 'colored'. 'pastel' originates from French 'pastel', and 'colored' comes from English use of 'color' (from Old French/Latin).

'pastel' came into English from French 'pastel', which in turn derives from Occitan 'pastèl' and ultimately from Latin 'pastillus' meaning 'a small loaf or paste'. 'color/colored' developed from Old French 'colorer' and Latin 'colorare' from 'color'. These elements were combined in modern English to form the descriptive compound 'pastel-colored'.

Initially 'pastel' referred to a paste or dye and later to the soft crayons and the gentle hues they produce; 'colored' has long meant 'having color'. Together the compound came to mean 'having soft, pale hues' in modern usage.