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