Colorful Books are actually what students are to deal with. They contain all the secrets the learner must get familiar with in order to gain good command over English language.
Red Book deals with the basic syntax features as well as the phrases and expressions for daily use.
Green Book walks the student in more sophisticated language structures. The learner study social habits in more details while enriching the thesaurus of all important phrases and expressions.
Blue Book welcomes those brave into the world of advanced English. Good students need them if they speak about hypothetical situations or speculate about probabilities.
White Book is the mother of the three above. It explains the underling principles that create English syntax rules. It is mainly a subject of study to those keen to obtain detailed insight into the inner work of English language.