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