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