What to plant?

At the front of our house we have a lawn surrounded on 2 sides by 2 small 12"high stone borders,behind that a stretch of soil 20ft long 3ft deep id like the brighten up this part of the garden with some nice spreading perennial plants,theres nothing in it at the moment other than a few weeds

Some advice,help much appreciated as always

 

What height do you want from the plants, flowering times, colours, etc, etc. How much sun does this area get?

There are thousands of herbaceous perennials to pick from once you decide what you want!

 

Well just really ground cover, i was thinking along those lines,no tall plants about 6" at most,thefront is in the sun a good 4 hrs a day,id like a colourful spread,purples,yellows reds,white etc if at all poss
Flowering times through spring to about october

thanks advice appreciated