"The kindergarten version of these lessons (blue book) spends more time on each skill. The kindergarten curriculum covers all consonants, short vowels, digraphs, blends, and rime patterns, with long vowel words being introduced in the later weeks of this curriculum. By comparison, the yellow book also goes further into long vowels and introduces R-controlled vowels, special vowel sounds, and multisyllabic words."--Publisher's website.