I think that the particular charity or group would select the colour that represents the aim of the charity?
I did however find these sites for you PB!!!
http://www.johnmaclennan.co.uk/charityribbons.htm
http://www.ribbonsandbows.org/?gclid=CITvpP3g54gCFQRCZwoddFNQrQ
My particular favourite would have to be the black and white ribbon, would co-ordinate well with SO many things 8)