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