I recommend this book. Morgenstern's FTP site contains papers and other coloring material. A presentation of the four color problem Mega Math, Educational. Harmonious Colourings and Achromatic Number is maintained by Keith Edwards and includes a bibliography. Routines for Solving Binary Constraint Satisfaction Problems by Peter van Beek.
Graph coloring is a restricted class of the constraint satisfaction problem.
The Stony Brook Algorithm Repository OR-Library Imperial College Management School.