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