The colouring of concrete is achieved through the use of cements, coloured sands, coloured aggregates and pigments (oxides). The basic cements used are grey, off-white and white. The use of cement colour will depend on the final colour choice, with grey cement generally used for darker colours moving to white cement for light colours. The use of coarse aggregates will have more impact visually because of their size. When an exposed finish is selected such as grit (sand) blasting or polishing, the coarse aggregates will have the most significant impact visually because of their predominance and sand colour will alter the colour of the surrounding cement matrix. Where the desired colour cannot be achieved by using cement, aggregate and sand selection, a wider range of colour can be achieved using pigments (oxides). Coloured precast elements can also have other finishes applied to them like etching, grit blasting, water washing, polishing and honing if requested.