One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,5,7)(3,8,4,6)(9,10,13,16)(11,17,18,14)(12,15,20,22)(19,23,24,21)(25,26,30,33)(27,34,36,32)(28,31,39,29)(35,37,40,38)(1,3,5,4)(2,6,7,8)(9,11,13,18)(10,14,16,17)(12,19,20,24)(15,21,22,23)(25,27,30,36)(26,32,33,34)(28,35,39,40)(29,37,31,38)(11,18)(14,17)(19,24)(21,23)(25,28,31,33,30,39,29,26)(27,35,38,34,36,40,37,32)(1,4,5,3)(2,6,7,8)(12,20)(15,22)(19,24)(21,23)(27,36)(32,34)(35,40)(37,38)(9,12,13,20)(10,15,16,22)(11,19,18,24)(14,21,17,23)(25,29,30,31)(26,28,33,39)(27,37,36,38)(32,35,34,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.