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)(27,34)(31,39)(35,40)(36,37)(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)(27,35)(28,32)(29,33)(30,38)(31,37)(34,40)(36,39)(9,12,14,11)(10,17,19,24)(13,23,15,22)(16,20,21,18)(25,27,29,34)(26,31,33,39)(28,37,30,36)(32,40,38,35)(2,6)(5,7)(9,13,14,15)(10,18,19,20)(11,22,12,23)(16,24,21,17)(25,28,29,30)(26,32,33,38)(27,36,34,37)(31,35,39,40)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.