I have classic mosaic red as well, and it is intense. I don't know how it produces this amazing color, but I enjoy it immensely.

Hi Dianne, it's done by hybridization, and the plants natural instincts to flower, but it can take years to get the desired plant, this is a very simplified answer, but you will get the gist, Derek.

the actual red colour is produced by specific pigments produced by the plant. the wavelength of light they reflect is then seen by your eye. there will also be green pigments [chlorophylls] present too.
there are many red pigments responsible for leaf, petal and fruit colour. Betalain is the pigment for the red of beetroots.
a few years ago my a-level students did a chromatogram of red leaf pelargoniums and they found 2 red pigments but we didn't go any further in identifying them as it was not the point of the exercise.

Thank you. A fascinating subject which can be applied to all flowers and fruit.