For commercial purposes, sunflower seeds are usually classified by the pattern on their husks.
If the husk is solid black, the seeds are called black oil sunflower seeds.
The crops may be referred to as oilseed sunflower crops.
These seeds are usually pressed to extract their oil and as a result produce plain sunflower seeds.
Black oil sunflower seeds are therefore those where the oil has not been extracted.
Striped sunflower seeds are primarily used for food; as a result, they may be called confectionery sunflower seeds. (source)
So can hamsters eat black oil sunflower seeds ?
Yes they care fine for hamsters to eat.
However, they are high in fat so be careful not to feed them too much as it is not good for them to eat too many black oil sunflower seeds.