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