Black is conservative, goes well with almost any colour except the very dark. It also has conflicting connotations. It can be serious and conventional. The colour black can also be mysterious, sexy, and sophisticated. Be careful using black with very dark colours. It can work, but if the colours are too similar they blend together. Black works well with bright, jewel-toned shades of red, blue, and green. Black is the ultimate dark colour and makes lighter colours such as yellow really pop out. Black and gray is a conservative combo as is medium or light blue and black.
White is purity, cleanliness, and innocence. Like black, white goes well with almost any colour. In most cases white is seen as a neutral background colour and other colours, even when used in smaller proportion, are the colours that convey the most meaning in a design. Use white to signify cleanliness or purity or softness. Some neutral beige, ivory, and creams carry the same attributes as white but are more subdued, less brilliant than plain white. Use lots of white for a summery look. Use small amounts of white to soften a wintery palette or suggest snow.