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