Any thick blanks will do. The darker colours tend to have less bleed-through, but lighter colours will reflect more light so you have more underglow.
All SA profile sets that I've tried block LED light completely, but they're mostly doubleshots, not blank. Some of the BSP, Gateron, Leopold and GMK sets (all thick Cherry profile) block the light well, too.
Signature Plastics DCS and DSA profiles let light through, as do the WASD caps.