I have dark blue grout on a shower floor. When it is wet, it is blue but when it is dry, it looks light gray. After cleaning and sealing the grout, it was dark blue until the sealer dried and was light gray again. How do you keep the grout the dark blue color we wanted?
If that grout color is not what you expected, there are dyes that can change it. Going from light to dark is easier than the other way, but check any good tile store for the dye. Easy to apply and last a long time.