How can I customise the keywords the preformatted text recognises?

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Our Q&A site for our command language would look great if the preformatted option could recognise our keywords. eg:

SAMPLE 1 100
GENR p1=1+nor(1)
SYSTEM 4 / DN NOCONSTANT COEF=beta
STOP

The capitalised commands shown are the ones we would like to color, however the commands are not necessarily capitalised. Where are the rules for colouring things like numbers and commands like 'end' coming from? eg:

1 2 3
end

Thanks in advance.