Picking the right grout colour for your tile can be confusing and frustrating if you do not know what you are looking for. The colour of the grout should blend into and complement the tile. The grout colour should not overwhelm the tile. Remember that the goal is to highlight the tile. After all, the tile is what you spent more money and time choosing, not the grout. The exception to this rule applies if you want a checkerboard look for your tile. Otherwise, the grout should be a neutral colour for neutral-coloured tiles and a darker colour for darker coloured tiles.
For neutral tiles, gather a few sample charts of neutral-coloured grout. Place the samples next to the tiles and see which grout blends and disappears the best.
Use black or dark grey grout for black or dark tiles.
Use grey grout for cool-coloured tile. Depending on the shade of your tile, use light- to dark-coloured grey grout.
Use brown grout for warm-coloured tile. Depending on the shade of your tile, use light- to dark-coloured brown grout.
Use either grey or brown grout with tiles that have both warm and cool colours. If you want to highlight the cool colours, use grey-coloured grout. If you want to highlight the warm colours, use brown-coloured grout. It is helpful to have a few samples of grout to compare against the tile.