Silica gel desiccant may be doped with a moisture indicator that gradually changes its color when the silica gel desiccant transitions from the dry state, to the wet state.
The silica gel blue is deep blue when dry and pink when wet.
The silica gel orange can be formulated to change from orange to green or orange to colorless.
By this way, the silica gel desiccant can be used as humidity indicator.
