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