I does not matter how much oil is on the parts before anodizing, the part is stripped of all contaminates before anodizing, if there is any oil present the part will not anodize very well at all

If this is happening at the color stage then the parts have not gone through a good enough acid neutralizer and wash before the color process

If this is happening after the color process, the anodizer needs to use a better sealing process, if the parts are not sealed correctly after the color, then the parts can pick up any contamination they come in contact with