Are you looking for something that will cover the wall all year, or just during the summer months?
If it's just for the summer try Sweet peas , Eccremocarpus scaber (Chilean glory vine), Ipomoea (morning glory) or even all three. They are annuals so will need replanting each year.
Perennials last from one year to the next so you could try honeysuckle (in a deep pot and keep the roots shaded), clematis - you can get both summer flowering ones (e.g. Clematis montana) and winter flowering ones (e.g. Clematis cirrhosa) or try a variegated ivy that will give colour all year from the foliage rather than flowers - it will hide the wall and could be used as a backdrop for other plants in front of it.

Many thanks for your excellent suggestions Rogerbee. I rather like the idea of the variegated Ivy and other plants in front. Thank you very much.

A word about ivy though - it will take over the entire pot in terms of its roots, so you'll need to restrict those by turning the pot out periodically (every couple of years) and pulling the ivy roots apart and replanting some pieces. It doesn't matter though, if the ivy's the only thing growing in the pot, it only matters if you want to grow anything else in with it.
Before you decide though, have a look at Trachleospermum jasminoides - google it if you want. Evergreen climber with very fragrant white flowers in summer.