Here’s Part 2, including stranded stitch dictionaries.
These are all useful, and it’s hard to recommend just one or two. They’re not listed in any particular order.
I tend to like creating pictorial motifs, so often I’ll use something I find in one of these to use for an accent motif, and tweak it til I get what I want so that it fits with my main motif. (I talk about modifying motifs in my Craftsy class, Custom Colorwork Techniques: Mitts.)
Stranded Stitch Dictionaries
Scandinavian Knitting Designs (Pauline Chatterton)
Alice Starmore’s Charts for Color Knitting. Awesome, very thorough resource.
200 Fair Isle Motifs (Mary Jane Mucklestone). Both this and 150 Scandinavian Motifs are fun because the swatches (yes, there are swatches!) are often shown in different colorways.
150 Scandinavian Motifs (Mary Jane Mucklestone)
Mittens Books (that you can use like a stitch dictionary)
Latvian Mittens (Lizbeth Upitis)
Latviesa Cimdi (Maruta Grasmane). Huge gorgeous book. Link goes to an English edition.
The Mitten Book (Inger and Ingrid Gottfridsson)
Mostly Mittens (Charlene Schurch)
Selbuvotter (Terri Shea)
Stranded Knitting Books (that include stitch patterns)
Bohus Stickning på nytt The Revival (Viveka Overland). Lovely to look at even if you don’t want purls in your colorwork.
Traditional Fair Isle Knitting (Sheila McGregor)
The Art of Fair Isle Knitting (Ann Feitelson)
Alice Starmore’s Book of Fair Isle Knitting