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)(11,16)(12,14)(13,15)(17,18,21,22)(19,20,24,23)(26,30)(27,33)(28,36)(38,40)(2,5)(7,8)(9,10,13,15)(11,16,12,14)(18,22)(19,24)(26,30)(28,36)(31,34)(35,39)(1,3,6,4)(2,7,5,8)(9,11,13,12)(10,14,15,16)(17,19)(18,23)(20,22)(21,24)(25,26)(27,34)(28,32)(29,30)(31,33)(35,40)(36,37)(38,39)(1,4,6,3)(2,7,5,8)(9,12,13,11)(10,14,15,16)(17,20,21,23)(18,19,22,24)(25,27)(26,31)(28,35)(29,33)(30,34)(32,38)(36,39)(37,40)(1,5,6,2)(3,8,4,7)(9,10)(11,14)(12,16)(13,15)(17,19)(18,20)(21,24)(22,23)(25,28,29,36)(26,32,30,37)(27,35,33,39)(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.