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