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)(25,26,31,34,30,33,29,39)(27,28,37,38,35,32,36,40)(1,2)(3,7)(4,8)(5,6)(9,11)(10,14)(12,18)(13,19)(15,21)(16,17)(20,24)(22,23)(25,27)(26,32)(28,33)(29,36)(30,35)(31,37)(34,40)(38,39) involution — undirected(2,6)(7,8)(9,12,13,20)(10,15,16,22)(11,18,19,24)(14,21,17,23)(25,28)(26,27)(29,38)(30,32)(31,40)(33,35)(34,36)(37,39)(1,3,5,4)(2,7,6,8)(10,16)(14,17)(15,22)(21,23)(26,33)(27,35)(34,39)(36,37)(1,4,5,3)(2,7,6,8)(11,19)(14,17)(18,24)(21,23)(25,29,30,31)(26,34,33,39)(27,36,35,37)(28,38,32,40)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.