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