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