There are two common varieties of sweet potato: one is white and the other is orange. There are also other colors of sweet potato.
Regardless of the color the name of this sweet potato is: Ipomoea batatas
Ipomoea batatas, commonly called sweet potato or sweet potato vine, is native to tropical America. It is a tuberous rooted tender perennial that has been cultivated for its orange-fleshed edible tubers for over 2000 years. It was reportedly brought back to Europe from the New World by Columbus. Today, the sweet potato is a popular root vegetable that is grown in vegetable gardens and as a commercial food crop throughout the world.
Although species plants and varieties grown as food crops have somewhat attractive green foliage, it is the more recently introduced purple-, chartreuse- and variegated-leaved cultivars that have transformed this vegetable into a popular ornamental foliage plant.
The OTHER ONE is: Solanum tuberosum
AKA The IRISH POTATO
Solanum tuberosum is commonly known in Canada as Irish potato, potato, white potato, yellow potato, red potato, and pomme de terre ( USDA - ARS 2014).May 24, 2015. [THESE ARE NOT KNOWN AS "SWEET POTATOES"
The white SWEET ones are hard to find in northern countries, sometimes.
To distinguish them in a northern hemisphere country, you can say:
white sweet potato because generally just sweet potato is the orange one in the north, also known as yam. And you don't need to say: orange sweet potato. I'll repeat that: In North America, yams are called sweet potatoes.
So, to refer to the others, you have to say: white sweet potato, purple sweet potato, etc.
If you are in Brazil, on the other hand, you just say: batata doce, which is the white or purplish kind because there no one knows the orange kind (generally speaking).
Here are the purple and white sweet potatoes eaten in Brazil. Please note: Traditionally, the white one is more popular than the purplish one.
Here is an entire article on this subject:
white sweet potato