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