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