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