Primer for interior wall?

[salsaysthis]

I'm painting an off-white colour on an existing grey/blue wall. Can I paint straight over or should I get a primer first?

Good quality emulsion will obliterate it, though you may need extra coats. You can use white vinyl matt, which will be cheaper than colours. If the old paint is silk, use silk again as matt will not adhere well.

When there is a strong colour or pattern underneath, you can use light grey as an undercoat, it kills the colour better.