When a colour is applied to a cross, the form is usually a basic Latin or Greek cross. The form bears no particular significance - simply easy to draw, easy to recognise, and doesn't detract the eye from the additional message given by the colour. When we see a red cross for example, we see either the colour red, or we see a sign of the humanitarian organisation. What we don't see, is a cross.
Coloured crosses are used for many different purposes and organisations. The Orange Cross for example, is used by several commercial ambulances and healthcare providers, and also political groups. Often these are seen as Lapel Pins. We haven't attempted to explain all the uses for each cross; the description given has been selected quite arbitrarily.
Neither do we include all the crosses that happen to be coloured; below are only the crosses that have particular significance because of their colour. (See also the symbolism of Liturgical Colours)