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