TA-15 Power Tube Replacement and Color Codes

I have an occasional gain drop in both channels of my TA-15 and believe that after 18 months of light use it may be time to replace one or both of the EL-84's. I checked my original tubes and they are a matched pair that are color coded GRN (Green). The local music store where I purchased the amp finally has some Mesa Boogie/Groove Tube replacements in stock after a few months of waiting. However, the only four EL-84's that they received are all coded GRY (Grey). I have done some reading up on the topic and the consensus seems to be that I would be OK to replace GRN with GRY, provided that they are indeed both matching as GRY (this would be the case). Looking at the color code chart, I see that GRY is directly next to GRN and both are rated a '5' on the 1 to 10 numeric scale that Groove Tubes uses. Could someone in the know give me some guidance as to whether or not I am OK to proceed as described, or must I indeed go back to Mesa Boogie and have a set of Green's shipped to Hong Kong for my TransAtlantic-15 if I wish to keep the great tone of the amp intact?

Thanks in advance!
HK Expat

The end user will notice virtually no difference with our different color codes. The color codes are for internal matching purposes only, and due to the tight range we select our tubes for - the difference between colors is minimal. You can read more here:

http://mesaboogie.com/news/2012/03/mesa-tube-color-codes-by-randall-smith/#more-3265

Thanks!

Thanks, Authorized Boogie! Appreciate your feedback.

HK Expat