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