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)(11,16)(12,25)(13,18)(14,20)(15,21)(17,24)(19,26)(22,31)(23,32)(27,40)(28,34)(29,36)(30,37)(33,39)(35,38) involution — undirected(1,3,6,2)(4,8,5,7)(9,11,15,24)(10,16,21,17)(12,26,23,14)(13,28,30,27)(18,34,37,40)(19,32,20,25)(22,38,39,29)(31,35,33,36)(9,12,14,11,15,23,26,24)(10,17,20,25,21,16,19,32)(13,27,29,22,30,28,38,39)(18,33,36,40,37,31,35,34)(1,4,6,5)(2,7,3,8)(1,5,6,4)(2,7,3,8)(9,13,26,38,15,30,14,29)(10,18,19,35,21,37,20,36)(11,22,12,27,24,39,23,28)(16,31,25,40,17,33,32,34)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.