904 or 316 does not always influence the color. I have Noob v7, v6, GMT V2, V3 (all 316 and some are whiter and others more gray-yellow), ARF Dj41, Op39 (904 and they look different between them), ZZF V2 (it was sold), EWF Dj41 ( 316 and very light color and white). I don't think that rep factories have a QC of the color of steel, it depends on the batch and depends on the never exact mix of types of metals will come out the darkest color, yellow, silver, white ... I also have to point out that my ARF and EWF are much whiter or lighter than my previous Gen sub.