1. deprived of color

e.g. colors dulled by too much sun
greyed with the dust of the road

Synonym: greyed

2. made dull or blunt

Synonym: blunted

3. having lost or been caused to lose interest because of overexposure

e.g. the mind of the audience is becoming dulled
the benumbed intellectual faculties can no longer respond

Synonym: benumbed