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