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