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