Hi Metalkitty,
Long time, no "see." Good to see you posting again. I'm not the color guru so I can only talk about my personal experience. Tracy is our resident color guru so she could definitely give you a better response than I. But, I had caramel highlights that didn't change color/tint despite the ACV rinses. I think that's b/c the high acidic level closes the cuticle rather than opening it and depositing a color. I had to play around with ratios to find one that worked for me but I love very little ACV to a whole lot of water.
I love ACV rinses for normalizing my scalp.
HTH!