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