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