Motorcycle/Scooter Licence Plate Colors

What do the different licence plate colors on Motorcycles and Scooter signify? Green, Orange, White.
Yesterday i saw this strange looking scooter. It’s white plate had blue lettering, as opposed to black. What kind of bike would that be?

Just curious.

Green’s 50cc, white’s between 50 and 250cc and yellow’s for over 250cc. Dunno about white with blue lettering though, although white lettering on a blue plate is military, I believe.