I seem to recall that the Redhawk was made in 45 Colt and that it had problems with cartridge rims slipping under the ejector star. There was quite a line up of Redhawks, 357, 41, 44, & 45. Sonnytoo is right.
In blue????? The only reference I can find in Ruger's dealer price sheets are three versions in stainless...a 5-1/2", a 7-1/2" and a 7-1/2" with rings. Further, I have never noted a serial number of a blue .45 Redhawk. If somebody's got one of these I can sure use the info for the reference. Please post a pic as well.
Ruger's model numbers wouldn't seem to support that they ever made a blue .45 Redhawk either, But ?????
Note that the high polish stainless models (with "G" at the front of the catalog number came out in 1993 or 1994 and the stainless .45 Redhawks were introduced several years later. The KRH-444 and KRH-45-4 (4" Redhawks in 44 Mag and .45) have only been around for the last few years. There aren't any model numbers in between there to substantiate a blue .45 Redhawk.