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