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