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)(16,20)(18,24)(21,22)(25,26)(27,31)(28,32)(29,37)(30,34)(33,38)(35,40)(36,39) involution — undirected(1,2,5,4)(3,7,8,6)(10,15)(12,22)(16,19)(18,23)(25,27,30,28)(26,31,34,32)(29,35,38,36)(33,39,37,40)(1,3,5,8)(2,6,4,7)(10,15)(11,20)(12,22)(13,24)(25,26,30,34)(27,32,28,31)(29,37,38,33)(35,39,36,40)(3,8)(6,7)(9,11)(10,16)(12,23)(13,21)(14,20)(15,19)(17,24)(18,22)(25,28,30,27)(26,32,34,31)(29,36,38,35)(33,40,37,39)(1,3)(2,7)(4,6)(5,8)(9,12,14,22)(10,17,15,21)(11,18,20,23)(13,19,24,16)(25,26)(27,32)(28,31)(29,33)(30,34)(35,40)(36,39)(37,38)(1,4,5,2)(3,6,8,7)(9,13)(10,18)(11,21)(12,19)(14,24)(15,23)(16,22)(17,20)(25,29,30,38)(26,33,34,37)(27,35,28,36)(31,39,32,40)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.