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)(11,17)(12,20)(13,14)(15,18)(16,22)(19,23)(21,24)(25,26)(27,29)(28,36)(30,31)(32,34)(33,37)(35,40)(38,39) involution — undirected(1,2,4,6)(3,5,8,7)(10,14)(15,17)(16,20)(23,24)(26,31)(28,37)(29,32)(35,38)(1,2)(3,5)(4,6)(7,8)(11,18)(15,17)(19,21)(23,24)(26,31)(27,34)(33,36)(35,38) involution — undirected(1,3,4,8)(2,5,6,7)(9,11)(10,15)(12,21)(13,18)(14,17)(16,24)(19,22)(20,23)(25,27,30,34)(26,32,31,29)(28,38,37,35)(33,39,36,40)(9,12)(10,16)(11,19)(13,22)(14,20)(15,23)(17,24)(18,21)(25,28,30,37)(26,33,31,36)(27,35,34,38)(29,39,32,40)(9,10)(11,15)(12,16)(13,14)(17,18)(19,23)(20,22)(21,24)(25,29,30,32)(26,34,31,27)(28,39,37,40)(33,38,36,35)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.