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