Grout repair

I have a tiled shower that needs minor repair to some of the grout (a few small cracks) and at the same time I'd like to darken the grout slightly.
The tile is glazed DalTile squares, the 1/4 inch grout is sanded Bosco Hydroment, French Gray. No sealer has been applied so far.
I have tried using AquaMix Enrich n' Seal on a small area and don't care for the resulting appearance.
Is there a sealing coating that is colored (dark gray) that can be applied over the existing grout? I will cut down the areas that are cracked and re-grout those first. If needed I can cut down all of the grout streets but I'd prefer not to do so.
The few product I have seen so far don't recommend use in showers.
Thanks, Boden
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