You want to freshen your home's look without breaking the bank. Paint is the most cost-effective way to do that.
But you still want to make good choices. The temptation is to grab a can of paint in the most trendy colour and slather it on the room that you walk into first.
Resist that temptation.
Look at your colour scheme holistically -- don't isolate certain rooms for colour update while neglecting others. You're not a museum, are you, or a Stately Home with a Red Drawing Room and a Blue Room?
If you're happy with your overall colour scheme, and especially if it consists of well-chosen neutrals, you can freshen the overall look with a feature wall: one bright wall, perhaps with a special decorative finish, to provide a counterpoint to the main scheme.
Then consider picking up that colour in soft furnishings, artworks, and ornaments. Soft mushroom walls look quite different with red accents to how they look with robin's egg blue.
The result? A fresh look with minimal expense and effort.