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