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