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