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