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