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