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