Sejs said:Darkvision is fooled by Hide/HiPS. If you had an ability that made you all black all over and you stood in a dark area.. Darkvision would see through that. If you had an ability that made you camoflaged with your surroundings by way of changing your color to match the color around you.. Darkvision would see through that.
Yes, just being mat-black in the dark doesn't help against Darkvision.
Spells/items that change your color do fool Darkvision. Cloak of the Elvenkind, Robe of Blending, and the Camouflage spell don't mention any change in their effects if the view is color-blind (such as Darkvision)