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