Do I need an undercoat everywhere if I'm painting a light colour over an existing dark and light wall in the same room?

[bobsmith2]

Hi,

I wanted to paint my living room but there are currently two different shades of blue - one is aqua blue and the other is a darker blue (royal blue). I've chosen a much lighter colour (off-white) to replace both colours. From my understanding, I'll need to add a white undercoat to the dark blue colour and then maybe 2 coats of the off-white. However, if I don't add the undercoat to the aqua blue do you think the colour difference will be noticeable? Or is it best to add the undercoat everywhere to ensure an even shade throughout?

Thanks!

 

[opps]

Are you using water or oil based paints? Walls or woodwork?

If walls, 2 or three coats of a decent emulsion (eg Dulux Trade, not Dulux) should cover dark emulsion if you additionally use a decent roller.

 

[JohnD]

A coat of grey matt will cover the old and give a regular base colour. It obliterates better than white or pale colours.

 

[Wayners]

Simple answer.
No.

 

[bobsmith2]

Great thank you all!

 

[Chivas69]

It may take 3 coats but there shouldn't be a need for any undercoat mixed in. I'm guessing it'd be water based paints? You need a decent emulsion rather than some thin cheap stuff.