This question seems to be popping up all over the place (not just that so-called "egg-as-persons" garbage in Colorado). It seems to be the anti-abortion folk's favorite tune these days (perhaps because every other tactic has failed to accomplish their ultimate goal of criminalizing abortion). First we need to establish exactly what we're attempting to define here when we are talking about the "personhood" of a fertilized egg. What does someone mean when they say "person" or "personhood" should apply to the zygote, embryo and the fetus? Do they mean an individual (existing as a distinct entity) human being? Or are they being more specific and speaking about the personality of a human being (as in "self")? Or maybe they are leaning more towards religiousness and are speaking of the unitary personality of Christ that unites the divine and human natures? Regardless of which definition is used, how can these possibly be applied to a fertilized egg?
So let us imagine (if you will) that these people are speaking of some philosophical ideal of "personhood", shall we? Considering that it is not plausible that people will put aside their personal belief systems in order to agree upon a philosophical definition of "personhood", it would appear to be illogical to argue from this perspective either.
I suppose next they'll be attempting to define the essential attributes of other concepts such as faith or love.
I find it ever so odd that these people not only wish to establish the egg-as-person but they loathe abortion so much so that they wish to give these eggs rights that a born person does not even have (more rights than any man, woman and/or child in this country). A child does not have the right to force it's parents to undergo any form of bodily invasion (including a blood test) without the parents consent. The law fully supports the right of a person to refuse to allow others to invade his or her bodily integrity.
These people can question the "personhood" of the zygote/embryo/fetus all they want... what they simply cannot do is question the "personhood" of a pregnant woman (regardless of whether or not her pregnancy is wanted).