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