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