Dark colours absorb more light than do light colours, removing light from a room and making the room moody or even hard to navigate. If you need to lighten a dark paint colour, you have a couple of options but also challenges. Dark colours are harder to work with than light colours. Dark pigments tend to be stronger and can overwhelm the pigments in lighter paint. If the dark paint is already on the wall, it is harder to cover with a lighter colour. Thankfully, there are workarounds that can lead to success.
Mix lighter paint with a bit of your dark paint to lighten a colour before painting, if your dark paint has not yet been applied. It is better to start with the can of lighter paint and add the dark colour to it if you want to lighten it a great deal. If you just need to lighten it a little, mix the lighter colour into the darker colour. Tube tints do not work well for this, as the relative amount of volume of pigment can be small compared with the amount of paint you use to paint a room. Mix the paint thoroughly before applying.
Use a tinted primer that is close to the lighter colour you are shooting for if you are lightening a colour already on the wall. Darker colours can take two or more coats to fully cover using standard house paint, so by starting with a cheaper paint that is tinted, you can get a good start on coverage, lay down a good base with a primer and save a bit of money. Go over the tinted primer with the lighter colour top coat and apply extra coats as necessary.
Use a high-quality paint to cover a dark colour that is already on the wall that you want to lighten quickly. Many paint lines make premium paints that are loaded with pigment and provide excellent coverage. The paint can carry a pricetag double that of regular paint, it but will save you time. You may still need a couple of coats to cover a colour like deep violet, but it will be fewer than if you had used a standard-quality paint.