Rob,
Download the Excel File i upload, and in search options choose WORKBOOK, and search for 5237 and 6628, without the 3, the number 3 means FLAT paint.
You will find 35237 it's Model Master MEDIUM GREY, equivalent to HUMBROL 145, Model Color 2537 (2 means semigloss), Xtracolor 15237 (1 means gloss) here's the tone color link
http://www.colorserver.net/showcolor.asp?fs=35237
Now search 6628 and you will find:
FS 36628 is Model Master CAMOUFLAGE GREY, Vallejo Model color 36628 and there's FS 36622 also Camouflage Grey, Humbrol 28 and Tamiya XF-19 (according to IPMS Stockholm)
Here's