Cinnamon is supposed to be lighter. You want to be able to distinguish it from normal grey. You could try breeding one of them to a bird with darker cinnamon, if you find one that is the color you are looking for, but cinnamon is supposed to be light to begin with.
Thanks DallyTsuka for siggy!
Snowball-whiteface cinnamon cock
Jeep-normal gray cock
Pebbles-whiteface pearl pied hen
Pankakes-PF cinnamon pearl pied cock