good eggs are usually bright white, no discoloration. If they are sunken in or stained then they may be under calcified. This is the rule MOST of the time, not all. I recently had my first clutch hatch and the eggs didnt look very good. They had brown stains and some parts didnt look as white as others. I didnt know if they were gonna hatch but they did and the babies are very healthy. However, I made sure the female had a break and was eating very well before I introduced a male to her again to asure proper calcium levels. I currently have eight eggs incubating and those were the only ones that looked bad.

-----
2.3.0 crested geckos (Speckles, Sandy, Squirt, Sunshine, Soldier)
0.1.0 Striped Cal. Kingsnake (Snuggles)
1.1.0 Green Iguanas (Sisco,Speedy)
1.1.0 Emperor Scorpions (Strongbad,Serenity)
0.1.0 Rose Hair Tanrantula (Sweets)
RIP Star and Sal