You need to get to grips with the rules of colour, in order to give your room a professional look. You need to decide which colours combine well and whether they are toning, harmonious or complementary.
Primary colours are three key colours which cannot be made from any other colour – Red, Blue and Yellow.
When mixing an equal amount of primary colour you get secondary colours, which are Purple, Orange and Green.
Red + Yellow = Orange
Red + Blue = Purple
Blue + Yellow = Green
When mixing a primary colour with a secondary colour, ratio of 2:1, you get Intermediate colours – Red-Orange, Blue-Green etc.
On the left hand side of the colour wheel you find the warm or hot and on the right hand side are cool or cold. It is useful to look at this when creating a cosier or lighter space.
This is the easiest group of colours, or non-colours to work with. Neutrals don't appear on the colour wheel and include Black, Grey, White and sometime Brown and Beige. Neutral colours all go together and can be layered, mixed and matched as no neutral colour will try to dominate over another.
Accent colours should be used as a complementary colour and in small quantities to lift or to give a 'wow-factor' to a colour scheme.
Using clashing colours used to be a 'big no' but when they are used carefully, then can look fantastic. If they are of equal tonal strength, you can mix them together. Don't stop at two clasing colours, you can easily use three or four but be aware that if one colour is paler or weaker, then the rest will get lost in the overall scheme.