How do i avoid grout shade variation

[faithhealer]

Just been caled back to a similar problem, thanks for the effo... what's it page Dave. BAL Limestone wide joint grout, just looks like it hasn't dried (been down 10 days) . Sunk a bit as well, too wet??? Customer wants the grout 'topping up', (like the display she said but didn't like to tell her the display didn't have grout in!!) is this wise without digging the stained grout out first! Thanks in advance John