Rubber gains much of its strength and its resistance to heat and light from the addition of carbon black. Hence the vast majority of rubber is black.
Coloured rubbers can be produced using other reinforcing fillers and suitable colouring pigments.
However, the changes that take place during curing, and the nature of the moulding process, make it difficult to maintain perfectly even coloration, particularly with pale colours. Silicone rubbers are the most suitable for achieving reliable and clean coloured mouldings, even with pale colours and translucents.
The finish of rubber can range from semi-gloss to extremely matt using the same mould, but it will always be less smooth and mirror-like than plastic. The matt, non-reflective nature of their surface means that coloured rubbers will have a different appearance to neighbouring “hard” materials.
Attractive appearances can be obtained by moulding a patterned surface into a component, such as a fine matt geometric pattern or “sparked” finish.