Type 2 grey anodize that has a brownish tint

Would anyone know why our type 2 grey colored anodize would come out with a brownish tint. We have a VERY picky customer that does not accept any color variation and we've had this problem before. We've changed out the dye, adjusted pH. Could cross contamination cause this?

How about a common rinse with either a dichromate seal or a chromate-based desmut? My thought would be that if the freshly anodized or dyed anodic coating were to come in contact with any chromate (even a conversion coating rinse), it would pick up the yellow/brown from the hex chrome and throw off the "gray" color. The other thought is that you may just be dealing with an alloy that anodizes to a yellowish tint - some of the 7xxx series have that wheaty color whereas 6061 doesn't show this. Anodically speaking - good luck!