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