We accidentally read the second book in this planned trilogy first: Red Side Story, but after reading Shades of Grey (#1268) by Jasper Fforde, much is explained that we missed the first time around. It's social satire at its best, so it really would make sense to read them in order.
Edward Russett is a young man on the cusp of discovering the strength of his color perception. The Ishihara will determine what your role in the community will be, who you are eligible to marry and other key factors. Once tested, the results cannot be changed. But Eddie's father has taken on a temporary assignment in East Carmine, far from home, and his life is turned upside down. Eddie is a Red, which in the color hierarchy is looked down upon by the Yellows and especially the Purples. But to be fair, everyone looks down on the Greys, the class which performs all the meaningful work in society. It doesn't take Eddie long to figure out who in East Carmine to be wary of, and who to cultivate.
When Eddie falls hard for a Grey, Jane, a totally unsuitable attachment (He is, after all, half promised to an Oxblood back in Vermillion, a big step up chromatically.) he begins to question many of the rules governing their lives. Why must things be done a certain way? And why are huge swathes of the past routinely eradicated? And that's a problem by itself, one which those above him socially are determined to eliminate. Can Eddie survive to make it to the second book? You'll have to read it for yourself to find out.
Where does Jasper Fforde come up with these ideas?