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