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