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