various 'coloring' can be added. There are some special grouts offered last time when I do-up my house..but ended up i still prefer the black or white options..

if you go to DIY shop and ask for acid to wash tiles, they will give you the type that is suitable for washing tiles. For sure this type of acid will eat into the grout if you pour direct onto the grout line.. In general, i used the acid to clean up certain tiles surface which has some cements left after the tiler finished the work...