How do I paint over dark blue walls?

Painting over dark blue requires proper prep to prevent the colour from showing through:

First, clean the walls – remove dust and grease for better adhesion. Then use a compatible primer / undercoat to create a stable even light colour to build upon. What is the difference between a primer and an undercoat - click here. 

Why does my grey paint look blue on the wall?

Grey paint can sometimes appear blue due to the naturally cool undertone colours of Greys. Many greys have blue or green undertones that can become more visible depending on lighting. The room lighting can make a big difference.  North-facing rooms or cool LED lighting can bring out blue tones in grey.

The surrounding colours can make a big difference – Reflective surfaces, furniture, or décor with blue tones can influence how the paint appears. If your grey looks too blue, opt for a warmer grey with beige or taupe undertones, or switch to warm lighting (you can easily change your bulbs to warmer kelvin to create a warmer space)

History of blue paints

Blue pigments historically were derived from the lapis lazuli, a semi rare stone prized by the early Egyptians. It was always too expensive to be used in everyday homes, so it was always know to be a luxurious and 'divine' colour. Ancient Rome used the same blue in frescos and murals, as well as decorative tiling. 

Georgian Blues: Blue persisted to be a prized colour until eventually synthetic blue was manufactured, allowing the masses to also use tones of blue. The standout blue in more modern times is the duck egg blue, used in the Georgian and Regency eras in the 18th and 19th century and persists in fashion and trends to this day!

Victorian love of blues: The Victorians really did start to embrace richer and deeper colour tones, especially when paired with heavy fabrics and deep mahogany furniture. Blue wallpapers featured heavily at the time, intricate blue patterns often used in kitchens or libraries.