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