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)(25,26,30,31)(27,35,36,32)(28,33,37,40)(29,38,39,34)(1,2)(3,8)(4,6)(5,7)(11,17)(15,21)(18,23)(22,24)(26,31)(28,37)(32,35)(34,38) involution — undirected(1,3,5,6)(2,4,7,8)(10,14)(15,21)(16,19)(22,24)(26,31)(27,36)(33,40)(34,38)(1,4)(2,6)(3,7)(5,8)(9,10)(11,15)(12,16)(13,14)(17,21)(18,22)(19,20)(23,24)(25,27)(26,32)(28,38)(29,33)(30,36)(31,35)(34,37)(39,40) involution — undirected(1,2)(3,4)(5,7)(6,8)(9,11,13,17)(10,15,14,21)(12,18,20,23)(16,22,19,24)(25,28)(26,33)(27,34)(29,35)(30,37)(31,40)(32,39)(36,38)(1,4)(2,6)(3,7)(5,8)(9,12)(10,16)(11,18)(13,20)(14,19)(15,22)(17,23)(21,24)(25,29,30,39)(26,34,31,38)(27,33,36,40)(28,32,37,35)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.