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