MudWings - Eggs are most likely shades of brown (maybe brownish-amber), and are sometimes blood-red, which then would give the dragonet the ability to withstand most affect of heat and fire.
SandWings - Eggs are carefully placed together in clutches, sometimes in the sand to keep warm.
SkyWings - Eggs are a pale color, likely red, orange or red-gold.
RainWings -Eggs have smooth, pale shells and are kept in any of the three RainWing hatcheries. The RainWings do not count their eggs. The exact color of RainWing eggs is unknown, though they might be colour-changing like the dragon itself. It is also possible that they can be pale shades of different colours, or white.
IceWings - Eggs are kept in freezing hatcheries or buried in snow.
NightWings - Eggs are described as ebony black in Moon Rising, and are shown with silver flecks in the updated Wings of Fire trailer. If placed under the light of a full moon until hatching, the egg will turn silver, giving the dragonet the power of mind-reading and/or seeing the future. Hybrid eggs in this case might look a little more different than the purebred eggs, due to the differences between the hybrid's parents.