I found this equation for estimating beer color:
SRM = 1.4922 [(MCU) ^ 0.6859] - for values of SRM < 50
Where MCU = Malt Color (dL) * weight (lbs) / volume (gals)
From a Brewing Techniques log:
http://www.brewingtechniques.com/brewingtechniques/beerslaw/morey.html
Andrew