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