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