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