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