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