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