Enh, reds from darks is less important, but given the number of reds that tend to bleed, that’s one of those higher level skills he can learn. Around my house (with three people), we have enough to do whites/lights, blacks, blue/green, and red every week. My general rule is “will this be worsened if it’s stained, or will this likely bleed and be bad for something else in the load?” And if the answer to either is yes, put it with like colors (I don’t give a flying fuck if white underwear is stained pink, but a white blouse? Oh yeah).