Photo used with Permission from NFFGRB
A good fawn is a light straw color with a darker coloring over the back, hindquarter, and flanks. It has a white belly, white around the eyes, under the nose and chin, inside ears, underside of tail, and on the toes and underneath of feet as well. The undercolor is also supposed to be white. Since many breeders use sandies to cross into fawns, many common problems that they are heavily faulted for are smut, lacing on ears, black "peppering", or very dark coloring. Blue undercolor also shows up, and is highly undesireable. Fawns may also cross into white (I don't know), but be careful that you aren't using whites from light grays, steels, blacks, blues, etc. Also be careful that fawns are not crossed into the "color" lines-i.e. black, blues, lt. grays, and steels.
GENETICS OF A FAWN:
A- B- C- D- ee en en
Fawns are quite similar to sandies with the one difference they have the non-extension gene or "ee". It is the most recessive of the gene series and can show up out of sandies and other colors hiding the "e". Most colors have the full extension or "E" gene but steels will have the most dominant of the series "Es" and the last gene which is one not natural to flemish is the harlequin gene or "ej" which is recessive to "E" but dominant over "e". The fawn is essentially sandy in all other gene series and is one reason why that is the only other compatible color.