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