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