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