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