I purchased a foundation a couple of minutes before typing this, and during the process of choosing which shade to order, I stumbled upon a post in Yahoo! Answers Australia wherein one makeup artist gave a full chart for shade comparison between Mac's Studio Fluid Fix and Revlon Colorstay Foundation.
Revlon Colorstay vs MAC Studio Fix Fluid - Color Chart
Ivory: NW15/NC15 (lightest shade of the ranges)
Buff: NC20 (best match for fair NCs)
Sand Beige: NC20-25 (with somewhat neutral undertones)
Nude: NC25 (with peachy undertones, definitely not for pinks or true goldens)
Natural Beige: NW20 (tends to run pink)
Medium Beige: NC27 (between Sand Beige & Golden Beige)
Fresh Beige: NW25 (with pinky undertones)
Golden Beige NC30 (with yellow/olive undertones)
Warm Golden: NW30/NC30 (with somewhat neutral undertones)
True Beige: NW30 (with pinky undertones - for Fresh Beige in Summer)
Natural Tan: NC40/NC42 (more neutral than Golden Caramel)
Early Tan: NW35 (with somewhat peach undertones)
Rich Tan: NW35 (with pinkish undertones)
Golden Caramel: NC40/NC42 (more golden than Natural Tan)
Toast: NW43/NC45 (with neutral undertones)
Rich Ginger: NW45 (very peachy-pink)
Cappucino: NC50 (slightly more peach than Caramel)
Mahogany: NW50/NC55 (the darkest of NWs, but not extremely peachy)
Mocha: NW55 (seems to be very cool toned)
Please keep in mind that the chart is just for your guide, it is still best to consult with the brand's in house makeup artist so they can give you the best shade that matches your skin tone. Also, please take note that this comparison chart does not apply to Revlon's Photoready foundation.
If you have any questions, feel free to comment down below or email me thru my contact form.