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