If you want to be more specific than "red mixed breed chicken," just label them as RIR X CQ chicks, which gives people specific information about the bird they are buying. If people ask what that means, explain that they are a mix of a RIR X a specific known hybrid mix, essentially a second generation mix with no predictable outcome whatsoever. There's nothing wrong with a mix breed chicken, as long as that is how they are represented at sale. They will be fabulous birds that will serve the purpose that most people want, which is to produce great eggs. It is also important to let people know that you cannot predict which will be hens and which will be roosters, so don't select based on the CQ's sex-linked qualities.
X 2 --- an alternative labeling would be red barnyard mix.