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)(11,19)(12,17)(13,20)(14,18)(15,16)(21,23)(22,24)(26,28)(31,33)(32,36)(38,39)(1,2)(3,6)(4,7)(5,8)(9,11,15,20)(10,13,16,19)(12,14,21,24)(17,22,23,18)(1,3,5,4)(2,6,8,7)(10,16)(11,20)(12,21)(18,22)(25,26,30,28)(27,33,35,31)(29,32,37,36)(34,39,40,38)(9,12,15,21)(10,17,16,23)(11,14,20,24)(13,22,19,18)(25,27,30,35)(26,31,28,33)(29,34,37,40)(32,38,36,39)(9,13,15,19)(10,11,16,20)(12,22,21,18)(14,23,24,17)(25,28,30,26)(27,33,35,31)(29,36,37,32)(34,39,40,38)(1,4,5,3)(2,7,8,6)(9,14)(10,18)(11,21)(12,20)(13,17)(15,24)(16,22)(19,23)(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.