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