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