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