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