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