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