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