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