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