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