B. salviifolia is a variable species with a range across much of southern Africa, usually found growing at altitude. The blue-flowered form is the most common in horticulture; it is not necessarily representative of the species having been selected for the flowers and attractive velvety foliage.
In the wild, this species is quite variable with respect to flower colour. A very different white-flowered form is also cultivated in the UK, although this is less commonly found compared to the blue-form. The foliage of the two forms is different and a comparison of the two types is shown below.
I've also been growing this species from seed collected in South Africa by Silverhill Seeds. The foliage of these seedlings resembles the white-flowered form, and the flowers are in shades of pale lilac or violet.