One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,4,6)(3,5,7,8)(9,10,15,18)(11,20,23,31)(12,17,25,32)(13,19,14,26)(16,27,30,22)(21,36,39,35)(24,33,28,34)(29,37,40,38)(1,3)(2,5)(4,7)(6,8)(9,11)(10,16)(12,21)(13,22)(14,27)(15,23)(17,29)(18,30)(19,31)(20,26)(24,37)(25,39)(28,38)(32,40)(33,36)(34,35) involution — undirected(3,7)(5,8)(9,12,15,25)(10,17,18,32)(11,21,23,39)(13,24,14,28)(16,29,30,40)(19,33,26,34)(20,35,31,36)(22,37,27,38)(1,3)(2,5)(4,7)(6,8)(10,18)(16,30)(17,32)(19,26)(20,31)(29,40)(33,34)(35,36) involution — undirected(3,7)(5,8)(9,13,15,14)(10,19,18,26)(11,22,23,27)(12,24,25,28)(16,31,30,20)(17,33,32,34)(21,37,39,38)(29,36,40,35)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.