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