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