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