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