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