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