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