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)(25,26,30,34,32,35,31,27)(28,38,37,29,33,36,39,40)(1,3,5,4)(2,6,8,7)(9,11)(10,14)(12,19)(13,18)(15,17)(16,21)(20,24)(22,23)(25,27,32,34)(26,30,35,31)(28,38,33,36)(29,37,40,39)(1,3,5,4)(2,7,8,6)(10,15)(11,18)(16,22)(19,24)(25,28,32,33)(26,29,35,40)(27,36,34,38)(30,39,31,37)(1,4,5,3)(2,6,8,7)(9,12)(10,16)(11,19)(13,20)(14,21)(15,22)(17,23)(18,24)(25,29)(26,33)(27,37)(28,35)(30,36)(31,38)(32,40)(34,39)(12,20)(16,22)(19,24)(21,23)(25,30,32,31)(26,34,35,27)(28,39,33,37)(29,38,40,36)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.