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