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