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