Wernick, Pinner, and Sheasby in The Surface Treatment and Finishing of Aluminum and its Alloys report on testing for dye penetration in an anodized layer. The bottom line is that dye (any dye) won't penetrate any further than 0.7 mils (0.0007") regardless of what you do. For dyeing purposes, there is no point in an anodize layer thicker than 0.7 mils.
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