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