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