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