An inexpensive way to brighten and refresh your shoes? New laces! More to the point, contrasting laces.
For standard, flat, sneaker-style laces I recommend Converse laces, which come in a few lengths and many, many colors. ~$2!
For sturdy, round, boot-style laces, check out Doc Marten’s. ~$3!
[Make sure to get the correct length]
before & after:
See what I mean?
(Which color would you go for with the doc martens? Tough call, right?)
N.B. New white laces tend to make broken-in shoes look especially tired.