Western Approaches colors are actually quite simple...
Western Approaches Blue is a sky blue...and Western Approaches Green is a pastel green color...the other color is white...
The best way I can describe it...if you have the paint program within Windows...open it, click on edit colors, and punch in the following numbers...
Red - 194
Green - 223
Blue - 228
With a Hue of 126, a saturation of 93, and a luminosity of 199. That will get you close and give you rough idea...another option, Luftwaffe RLM 76 is pretty close. The Munsell Code is 5B/5/2
For WA green, try the following:
Red - 111
Green - 200
Blue - 139
Hue of 93, saturation of 128, and a luminosity of 146. Munsell Code is 5G/7/6
Now, obviously, your monitor will display colors differently than mine...so it's subjective at best. However, my monitor has a pretty good color balance (desktop publishing variety) so I'm confident that these colors are really close. Hope that helps.
Jeff