Washes and blends will wash to the selected background color or pattern.  For example, washing in 50% red with a blue background would result in purple.

Washes and blends will wash to black.  For example, washing in 50% red would result in dark red.

Washes and blends will wash to white.  For example, washing in 50% red would result in pink.

Washes and blends will wash to the underlying image.  For example, washing in 50% red would result in a pixel 50%, and 50% its old value.