Green’s Dictionary of Slang

candy adj.2

[? resemblance to transparent boiled sweets]

(US Und.) of dice, transparent.

[US](con. 1890s) ‘Animated Dominoes, Dice’ at Old and Sold [Internet] Transparent, or ‘candy,’ dice were ten dollars and much favored by crap sharks, for, since the metal was in the concave spots, they defied even close inspection.