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)(11,12)(13,16)(14,17)(15,18)(19,20)(21,23)(22,24)(25,26,30,33)(27,34,28,31)(29,37,38,32)(35,39,36,40)(9,11,15,13)(10,16,18,12)(14,19,22,21)(17,23,24,20)(25,27,30,28)(26,31,33,34)(29,35,38,36)(32,39,37,40)(1,2)(3,5)(4,6)(7,8)(25,26)(27,34)(28,31)(29,32)(30,33)(35,40)(36,39)(37,38) involution — undirected(3,7)(5,8)(9,12,15,16)(10,11,18,13)(14,20,22,23)(17,19,24,21)(25,26)(27,31)(28,34)(29,32)(30,33)(35,39)(36,40)(37,38)(1,3)(2,5)(4,7)(6,8)(9,13,15,11)(10,16,18,12)(14,19,22,21)(17,20,24,23)(25,28,30,27)(26,31,33,34)(29,36,38,35)(32,39,37,40)(1,2)(3,5)(4,6)(7,8)(9,14,15,22)(10,17,18,24)(11,19,13,21)(12,20,16,23)(25,29,30,38)(26,32,33,37)(27,35,28,36)(31,39,34,40)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.