Can you tell visually if mole sieves are saturated with water?

Some of the 3Å sieves in the above image have turned a darker color than the others. Does this mean they are loaded up and no longer pulling water from the solvent?
And if you can't tell visually when they are past their prime, what is the general rule of thumb re: their use?
Can I bake them in the oven to drive the water out, and re-use them? If so, what temp., and for how long?
Thanks.