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