The color of your gray background is:
HTML, #CCCCCC;
RGB= Red 204, Green 204, Blue 204;
CMYK = Cyan 24%, Magenta 16%, Yellow 16%, Black 1%
You should be able to use one or more of the definitions in your photo editing program - usually you just click on the background indicator and it will give you a menu with a choice of actual colors or the ability to enter one or more of the above definitions (you only need one - they are all the same color, just using different color models).
It that doesn't help, let me know what program you're using for photo editing and I'll see if I can tell you how to set it up.