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