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