Mastic over grout

[Surftuzzer]

About 36 hours after grouting a shower with a light grey grout, I ran some clear silicon down the vertical corners. The grout under the silicon now looks almost black (and has stayed like that for 3-4days now). So will the grout dry out back to light grey again at some point?

 

[yorksbuilder]

It will stay dark. Mapei do coloured silicone to match to their coloured grouts

 

[opps]

As above. It sounds like you used clear silicone. The grout colour will not revert back to light grey.

An epoxy grout would not have changed colour, but they can be a pig to work with.

Unfortunately, you need to try to remove the silicone and then use the right colour. From memory, Mapei sell at least 4 shades of grey