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Results found in several dictionaries: Collins, Collaborative Dictionary
slate-blue  adj de color azul pizarra

Collaborative Dictionary     English-Spanish
! i feel blue q. Estar triste, deprimido, estar bajo de moral.  
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'slate-blue' also found in translations in Spanish-English dictionary
borrón y cuenta nueva pref. clean slate Reverso General Dictionary 
la bacaladilla nm. blue whiting Reverso General Dictionary 
azul claro exp. light blue Reverso General Dictionary 

"Collins Spanish Dictionary 8th edition published in 2005 © William Collins Sons & Co Ltd 1971, 1988 © HarperCollins Publishers 1992, 1993, 1996, 1997, 2000, 2003, 2005"