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