What color are fertilized bearded dragon eggs when first laid?

I have two bd females, that are 3 yrs old, we recently introduced a 3 yr old male bd, back on March 16th, 2011. One of our females laid a clutch of eggs, on April 18th, 2011, total of 22 eggs. Our females have laid eggs, earlier this year, before we got our male, and they were infertile. So, my Q? is, how do I know (since I have not "witnessed" any breeding), whether these eggs are fertile or infertile? The previous eggs, have been yellow, and eventually turn hard. So, how do I know, if these recently laid eggs are fertile or infertile? Are fertile eggs typically white, when first laid, or do they turn white, after awhile? I have tried the "shine the light" method, on a few of the eggs, and have seen no tale-tale signs, {i.e. no object and no veins). So, could you please tell me, how do I really know, if they are fertile or infertile? The bd care sheet, from LLLReptile, says to go ahead and incubate them to "full term" (i.e. 2 months), just in case, or until they mold, etc. Thank you, for your time, consideration, and cooperation, I truly appreciate it.