With the Rhode Island Reds as mothers, I think you would get green, not the darker shade that people are calling "olive." To get olive eggs, you would want to use a hen that produces very dark brown eggs (Marans or Welsummer are the usual choices.) Rhode Island Reds do not usually have the genes to produce eggs that dark.
But that is assuming the chicks have the blue egg gene at all. If the rooster hatched from a blue egg, then you know his mother had at least one blue egg gene. But you don't know if she gave it to him, or if she also had a gene for not-blue eggs and maybe gave that to him instead. And you also do not know what egg color genes he got from his father.
So the rooster may have no blue egg genes. Crossed to a Rhode Island Red hen, that would produce daughters who lay brown eggs.
Or the rooster may have one blue egg gene. With a Rhode Island Red hen, he would produce some daughters that lay brown eggs and some that lay green eggs (roughly equal numbers each way.)
Or the rooster may have two blue egg genes, so he would have to give one to every chick he sires. If that is the case, crossing him to Rhode Island Red hens will give daughters that lay green eggs, with no daughters laying brown.
If you are impatient to know how many blue egg genes the rooster has, there is a DNA test:
https://iqbirdtesting.com/blueegg
But if you intend to hatch eggs and raise chicks anyway, no matter what color eggs they lay, then you could just wait to see what color his daughters lay, and that will give you the answer without paying for the test.
