There are gradients of color but the RIR only comes in red. The feathers of the RIR range from a lustrous deep red to almost black and the tail is mostly black.
There is a New Hampshire Red that was developed from the RIR in 1915. They are also red but lighter than RIRs sometimes including yellow feathers. While RIRs can have either single or rose combs, NHRs only have single combs. While the RIR is a egg producing breed, the NHR is a dual purpose breed, has a deeper broader body. Even so the NHR does come in standard and bantam.
I say this to point out that a lighter colored feather on a single comb RIR could be confused with a NHR until you look at the body characteristics. The NHR is significantly larger.
The other hen that is frequently confused with RIRs is the Production Red. True RIRs are very dark in color with the black tail and neck feathers. Production Reds tend to be lighter in color and frequently will have white feathers because they have been cross bred with, of all things, white leghorns, to increase egg production. They will have a slighter build than RIRs because of this as well.
