The Flood Fill tools fill the active or visible layers with color, speeding up the painting process or working as a mask. As always, if the settings aren’t to your specifications, change the tolerances to create the effect you want.
Before using Flood Fill or Flood Fill All Visible Layers, change the tolerance to determine the range of color values affected when flooding a region with paint. The minimum tolerance, 0, selects and fills only pixels of that color value. The maximum tolerance, 255, selects and fills all pixels regardless of the region. When you set a tolerance of 10, then select a pixel with the color value of 20, the tool floods all pixels with a color value ranging from 5 below to 5 above. However, if you increase the tolerance to 200, the tool floods pixels with a color value ranging from 0 to 20 and 20 to 200.