If you look at other photos of lighter colored females, their gravid spot may not be so dark. Albinos obviously aren't. Perhaps overall pigmentation, as well as health, tank decore (certainly gravel hue), mood and age are all factors in the mix.

As miskairal suggested, she does seem to be aging. Guppies are not long lived fishes. One to two years is about it. The higher the temperature, the shorter the life span.

Another way to check her relative health and potential for parenthood would be to gently herd that female into a jar. Hold the jar and shine a flashlight through her from the back. This "candling" can show if she has fry in her. That is also a good way of sexing egglayers or to determine how ready a female egglayer is for breeding.

Sometimes it is just fun looking at Guppy photos. Of course your official reason is to compare others with your female. ;)

I was frustrated in that this site's search function gave a lot of hits for guppy photo, guppy image, guppy photos. There wasn't much in most of the hits on photos though. Google wasn't much better. I know that a couple of guys (Parttimer? PeterW? everb?) recommended some great visual sites and I can't find their post on the subject.

Below are some other sites which have been mentioned (or should have been mentioned) from time to time. By no means is it comprehensive - do a Google image search for Guppies and see what I mean. Still the following are fun to browse. Some have many pages, so look around and check their links to other sites.

Undoubtedly others who happen upon this have other favorite guppy images. Please share the URLs.

Thanks and all the best!
uncle scott

http://www.tropicalfishintl.com/guppy.htm

http://www.ne.jp/asahi/medaka-ken/k.t/framepage5.html

http://www.world-guppy.de/

http://www.laurellakeguppies.com/

http://www.ifga.org/

http://www.deltaguppies.com/

http://www.arihood.com/azgenetics/guppycolors1.html

http://www.ne.jp/asahi/medaka-ken/k.t/framepage5.html

http://www.ifga.org/guppy_store/gs_roebuck.htm

http://www.guppy-art.de/galerie01.htm

http://www.imagestation.com/album/?id=4288225435