What Colours Are Available To Use With a Custom Number Format EXCEL
In addition to the 8 named colors you can also use [ColorX], where X is a number between 1 and 56. The named colors are identical to [Color1] to [Color8].
A quick way to see all the colors provided is to run the following in the immediate window in VBA (preferably in an empty workbook):
for x = 1 to 56:cells(x,1) = "AAAA":cells(x,1).numberformat = "[COLOR"&x &"]@":Next x
According to this, There are only 8 colors, the list is:
[Black]
[Green]
[White]
[Blue]
[Magenta]
[Yellow]
[Cyan]
[Red]
It applies to Excel 2016, Excel 2013, Excel 2010 and Excel 2007