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.