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