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