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