The 7 colours of the rainbow
The seven colours of the rainbow are the "visible" part of the electro-magnetic spectrum - they are visible to (or can be seen by) the human eye. A rainbow is what we sometimes see in the sky when the sun is shining and it is raining somewhere at the same time.
|ultra-violet||not a colour - invisible to the human eye|
|7||violet||These are the 7 colors of the rainbow - the "visible spectrum" (visible to the human eye)
|infra-red||not a colour - invisible to the human eye|
This mnemonic can help you remember the colours of the rainbow and their order: Richard Of York Gave Battle In Vain
Black and white
Technically, black is not a colour (it is the absence of all colours), and white is not a colour (it is a combination of all colours). Grey also is not a colour since it is a mixture of black and white. But in normal language we usually describe black, white and grey as colours.
Three more very common colours
Brown is a very common colour and occurs a lot in nature. Silver and gold are shiny "metallic" colours.