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)(11,20)(12,25)(13,30)(14,18)(15,19)(16,22)(17,27)(21,36)(23,32)(24,35)(26,31)(28,34)(29,39)(33,37)(38,40) involution — undirected(1,2)(3,7)(4,6)(5,8)(9,11,15,24)(10,16,19,32)(12,26,27,38)(13,23,14,22)(17,33,25,36)(18,35,30,20)(21,28,37,29)(31,39,40,34)(2,6)(3,4)(7,8)(9,12,13,28,15,27,14,29)(10,17,18,34,19,25,30,39)(11,21,22,38,24,37,23,26)(16,31,20,33,32,40,35,36)(1,3,5,4)(2,7,8,6)(12,27)(17,25)(21,37)(26,38)(28,29)(31,40)(33,36)(34,39)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.