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