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