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