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