Summarize this article:

White is the most popular color for togas, but if you don't like to wear white, you could try an off-white color, such as ivory or pale gold. If you want something more striking, then maroon or green are good options too. Make sure that your bra is strapless too, otherwise you'll spoil the whole strapless look! This is only if your shorts and tube top are white. If they are a different color, match the bed sheet to them instead.  Make sure that the narrow edges of the bed sheet match up. If you are very tall, then you may want to fold it askew so that 1 edge is longer than the other. If the bedsheet is too narrow to wrap around your torso, fold it lengthwise. A leather belt would work just fine here, but you can also use a thin leather or gold cord. If you choose the latter, consider wrapping it a few times around your waist so that it makes an X. This style is very simple and elegant. You can make it look fancier by wearing a gold necklace or collar. The lack of shoulder straps will help make it stand out!

Summary:
Put on a white tube top and a pair of matching white shorts. Fold a white, solid-colored bed sheet in half widthwise. Tie a belt or cord around your waist to cinch and secure the toga.