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