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