Use 'colour in' when being precise in applying colours within defined areas or outlines.

Artistic Precision

The phrase suggests creativity, so choose any colour that you feel is right for the picture.

Creativity Encouraged

'Colour in' is commonly used in school settings or in activities related to children.

When 'colour in' is used, it suggests adding layers or enhancements to a story or character.

Be cautious not to 'colour in' too much; excess details may overwhelm the main narrative.

Use 'colour in' to make a text more vivid and engaging, like adding colour to a black and white image.