My understanding is that afterburner flame color mostly comes down to temperature. American jets have blue afterburners, too, at lower power levels, it turns orange towards the upper limit. Maybe Russian jets typically have the maximum dialed down, or that's just the limit of the particular design. I know that it is (or was, at least, 30 years ago) pretty common in the US for Air National Guard fighters to have stops installed when they're training, and not on alert status. IIRC they were typically capped at zone 1 (out of 5 available).