When trying to implement BBCode with creole the two obvious omissions are:

[color=orange][/color]
[size=7][/size]

For obvious reasons creole should not have 'color'.

More universal but less easy to digest would be '#ff0020 for the colour and "+" or "-" to indicate bigger or smaller sizes than standard for fontsize. As for actual fonts, Creole should not specify a font but there may be need to change from a  proportional font like Arial to a mono-space font like courier.