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