A number of potato varieties exist, some easily identified by skin or flesh colour. While there are no potatoes with zero starch, some have a low starch content. You can compare starchiness by cutting into a potato with a knife. High starch potatoes have a milky white residue that remains on the knife. Lower starch potatoes leave little or no residue when cut.
"New potatoes" is a term that typically applies to all potato varieties that are harvested before reaching maturity, although many varieties are given the name simply due to their small size. True new potatoes are generally less than 2 inches round, and the skin is soft. Because they are harvested before their sugar has turned to starch, new potatoes are low in starch and have a high water and sugar content.
Fingerlings have a thin skin and are often cooked unpeeled. They get their name because they resemble a thumb, growing to about 3 inches long. Fingerling varieties, which include Russian banana, white and purple Peruvian, are low in starch and have a yellow, waxy flesh.
Yellow potato varieties, such as Yukon Gold, Nicola and Carola, are round or oblong shaped potatoes with thin skins that are yellow-brown in colour. They have a low to medium starch content and a moist texture. Yellow potatoes have a buttery taste and are ideal for recipes that require boiling, steaming or roasting.
Round whites, which include Atlantic, Kennebec and Superior varieties, have a freckled light brown skin. The flesh of round whites may be waxy or creamy. Round whites are ideal for boiling, roasting and frying, and they tend to hold their shape after cooking.
Because they are small, round reds are sometimes called new potatoes. Typically they are round with a reddish brown skin and a dense white flesh. Round red potato varieties, which include Norland and Red Pontiac, are low in starch and taste sweeter than round white potatoes. They are ideal for boiling, roasting and grilling.
Heirloom potatoes come in a couple of interesting colours. Purple and blue potatoes have blue-grey or purple skins with a bluish-coloured flesh. These potato varieties, which include All Blue and Purple Peruvian potatoes, are also called heirloom potatoes and have low starch contents. They're ideal for boiling, steaming, roasting, frying and for salads. Other heirloom varieties include Huckleberry and Blossom potatoes, which have red skin and flesh. These are also low in starch.