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