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