Then post THESE to make your point: not a color spectrum.
So you are allowed to post abstractions (A, A', A'', A'''. ...) but I am not? That's an honest form of debate.
http://www.pbs.org/wgbh/evolution/library/05/2/l_052_05.html
http://www.pbs.org/wgbh/evolution/library/05/2/image_pop/l_052_05.html
http://en.wikipedia.org/wiki/Ring_species
http://www.actionbioscience.org/evolution/irwin.html
http://www.don-lindsay-archive.org/creation/ring_species.html
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11838767&dopt=Abstract
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&list_uids=15255043
http://www.zoology.ubc.ca/~irwin/GreenishWarblers.html
http://www.zoology.ubc.ca/~irwin/
http://www.talkorigins.org/indexcc/CB/CB910.html
http://www.bioone.org/perlserv/?request=get-abstract&issn=0014-3820&volume=055&issue=05&page=1029
http://www.bioone.org/perlserv/?request=get-abstract&issn=0014-3820&volume=054&issue=03&page=0998
http://repositories.cdlib.org/lbnl/LBNL-54692/
http://www.sciencemag.org/cgi/content/abstract/307/5708/414
http://www.findarticles.com/p/articles/mi_m1200/is_3_159/ai_71352449
http://ucsdnews.ucsd.edu/newsrel/science/mcwarbler.htm
http://calladus.blogspot.com/2005/09/black-or-white-highway-ring-of.html
http://users.aber.ac.uk/fee3/ring%20species%202.htm
http://www.madsci.org/posts/archives/sep99/936393054.Ev.r.html
http://darrennaish.blogspot.com/2006/02/no-no-no-no-no-herring-gull-is-not.html
I'm going to assume you will not read these links, which is really too bad, because they contain something that creationists claim doesn't happen in science -- an instance in which a well established "fact" is overturned by lots of research and careful reasoning.
Of course this doesn't change the larger fact that species is a fuzzy concept with not much basis in biology. Or that evolution progresses by tiny changes, so that transitions cannot be seen in human time scales.
You cannot see the relevance of the color gradient, apparently because you have been lied to about how evolution works. You have gotten too much of you education about evolution from Hollywood movies.