No worries,if you're still worried after giving it some time another option is to see if putting a sealer on it will uniform the colour (obviously test in a corner first)
OK I'm going to say it. You are a professional tiler yet you have never seen grey grout dry out before? You took a photo an hour after grouting and are having a fit because "IT'S DRYING"
OK I'm going to say it. You are a professional tiler yet you have never seen grey grout dry out before? You took a photo an hour after grouting and are having a fit because "IT'S DRYING"