When choosing the colour and material for your bi-folds there are a few things that you need to consider.
Materials already used throughout your home
In order to make sure your bi-folds enhance the style of your home, take into account the materials you already have. Do you have timber furniture? Is it more traditional or more contemporary? This should help you decide which route you would like to go down, as a more modern contemporary kitchen would probably suit a painted bi-fold, whereas a more warming rustic living room will accept an Oak bi-fold easier.
Colours already used throughout your home
If you currently have quite a neutral home almost any style will go including natural and painted timber. If you have a certain colour scheme, you may wish to include this in the colour of your doors. For example you could have a contemporary style interior with hardwood floors which suit an Oak finish rather than more neutral colours. However, it works both ways with a traditional home leaning more towards a painted finish, the best example for this is Cotswold green.
External faces of your property and the style you are going for
Ensure you consider what you would like the bi-folds to look like from the outside, as well as the inside. If you already have white or painted windows, you may want your doors to match. In the same way that if you had natural timber windows, you may prefer to have natural bi-folds.
You could definitely get away with having Oak doors with painted windows, but the other way around may cause some conflicts. However, if you like the look that much I won’t tell if you don’t.