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