Blind is a mechanic that can be applied by enemy spawns to hide orbs from view. There are two types of blinds: a Traditional Blind and a Super or Sticky Blind.
Regular Blind
A traditional blind simply darkens the entire board. If the orb is tapped, it will briefly show its color, and when the orb is moved, it will become fully visible again. These are usually fairly harmless.
Super Blind
Super/Sticky Blinds will darken a portion of the board and will display a number on top of the orbs affected. This number decreases every turn. When it reaches zero, the orbs will become visible again. Sticky blinds do not become visible when moved, but may still be tapped to show its color before you begin to move it.
Handling Blinds
Both types of blinds can be resisted with the 
Resistance-Blind or the 
Resistance-Blind+ awakening. This can be found on cards such as Reincarnated Diaochan
or on weapon assists like Avidya Saber
.