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