If you said Digitalis or Foxglove, you win the prize. You can easily encourage the bloom colour of your choice by only allowing those colours you like to set seed and deadheading all others. In a few year, you'll have a custom coloured garden. D. grandiflora is the only one of the family that is truly a hardy perennial in our climate. All others act as biennials, growing the leaves their first year and flowering the second.
Biennials die after flowering.
If you allow them to self seed, you'll have a never-ending supply. I start mine by sowing them directly in the garden in the spring. I do not cover the tiny seed, they'll work themselves deep enough after the first rain or sprinkling. I get better and cheaper plants doing it this way rather than purchasing the plants already started. A plant that is quite sexy right now is a full or part shade lover - we're talking Christmas Rose or Helleborus niger.