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