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