Before you decide if tile paint is the way to go, consider these things:

Say for example the tiles are red and black, what colour is the grout?

When you paint the tiles, you will be painting over everything, including the grout, so you won’t have a different/contrasting grout colour.

Are the tiles in a high traffic area
It is a floor or a shower for example.
Tile paint will scratch quite easily and depending on the quality, can't stand up to water exposure for years and years.

In our opinion it is a good temporary fix and can be a complete success in the right area that will transform a space quickly and is relatively cost effective.

Here is what you will need for a successful tile paint job:

180/240 grit sandpaper
Hoover/dustpan and brush
Damp cloth
Small foam roller
Tile paint ***

Make sure you prepare the existing tiles properly. This is essential for good paint adhesion.
Lightly sanding the tiles with the 180/240 grit sandpaper to take the gloss off the glazed finish will prep the surface well.

Next, clean them thoroughly with a hoover/dustpan and brush, and a damp cloth so there is no dust and make sure you use the correct primer and paint made specially for tiles***

After you have cleaned off all the dust, follow the instructions on your tile paint to apply it.
We recommend using a foam roller to apply the paint quickly and smoothly.

Allow to dry and apply a second coat after the recommended recoat drying time.

If you are looking to lighten and clean the space up, go for a nice white/neutral colour.
Tile paint colours have got more exciting in recent years but can be a bit limited.***

You may have to do a few layers depending on the original tile colour.
Painting tiles can look great and it is a cost effective way to have that “insta-change” makeover.  

Remember you can tile over tiles too.  If I was you I would do a cost comparison on tiling versus painting, then have a look at the available tile paint colours and decide what is best for you.

***You may want to have a look at Fusion Mineral Paint. This paint is taking the Upcycling world by storm.
We have a blog post all about it here.

It is excellent for painting onto tiles after using their "Ultra Grip" Primer and it's available in an excellent range of colours!

My favourites are Tuscan Orange (DIY Doers of course) and the beautiful Midnight Blue
Tuscan Orange

Midnight Blue

You can purchase it from Muck N Brass in Forest Hill, London
and across the country at various stockists. Check the Fusion website for details.