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