ReadPixelFast Color

Hi, I am having trouble understanding the readpixelfast command,

i have drawn something, locked the buffer run this

pixelcolour% = ReadPixelFast (220, 100)

then unlocked the buffer and printed the pixelcolour% and i get some wierd results. for example pure white is -1.

am i using this command right and if so is there anyway to convert it to a proper useable rgb value?

red% = PixelColor% Shr 16 And 255 And Shl 0
green% = PixelColor% Shr 8 And 255 And Shl 0
blue% = PixelColor% Shr 0 And 255 And Shl 0

+BlackD

thanks, it works fine but I didn't use the code "and shl 0" on the end of any.