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