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