The colors on this website make more sense. Red has traditionally represented leftist political parties, while blue has represented conservative parties.
Actually switching red with blue wouldn't be that hard. It would be simple enough to use IrfanView or another program to batch process the images from RGB to BGR. But it would play havoc with the colors used for other parties.
Ideally, the colors would be user customizable, and if Dave ever decides to implement a switch he probably ought to do that.
Doing a download and then reload of so many images stacked in different directories would be tough enough, before one even considers user images and user contents, changing scripts (unless the color part is a called function), etc. Not to speak on Dave's behalf, maybe I overestimate the difficulty, but it seems like a tough go.