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