I have sent a few colored silver Ghana coins to be graded, with the COA, yet they cannot be graded according to NGC policy. 

See what you think?

The reply:

Thank you for your email. Unfortunately, we are not able to grade coins that have been colored or altered in any way after being produced from the mint per our grading policy. The alterations may have an effect on the metal and therefore we cannot guarantee the grade and condition of the coin. Thank you

I rest my case.