Hey B,
I don't have any Columbian Rocks or eggs, though I have been looking for a year. Where did you get yours? There is a member in Georgia (I think) that has some young CRs you may contact. "Yard full 'o Rocks" bought 25 from Dunlap Hatchery in Idaho. As far as I know the eggs are like any Plymouth Rock, medium to large, brown to light brown.