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