Does protection from a color prevent damage from a colorless source?

Protection from a color (e.g., protection from red) grants four shields, often remembered as "DEBT": the permanent can't be Damaged, Enchanched/Equipped, Blocked, or Targeted by sources of that color (CR 702.16b).

A colorless source — such as a colorless artifact creature or a colorless spell — has no color at all (CR 105.2). Because it isn't the protected color, none of the four protections apply, and the colorless source can deal damage, block, target, or attach normally.

To be protected against colorless sources specifically, a permanent would need "protection from colorless" (which some cards do grant), not protection from a color.