can you apply yellow chromate over a clear chromate?

[pauloe]

If you have a part that has been finished with a clear chromate, can you just apply a yellow chromate to give the part a yellow color?

[Shvegel]

I have had some success and some failures.  I would imagine a clear chromate without any further surface treatment would take a yellow chromate just fine.  I think the trouble arises when you have a production part that has been oiled or coated to keep it nice during shipping.  I try and if it doesn't work I replate the part then yellow chromate it.