Red = Key of whistle being played (for example, the first line shows the D major scale played on a "D" whistle)
Blue = Note that is not actually a part of the Major scale for that whistle, but is used quite often
Grey = "Secondary key" (for example, a "D" whistle will also play easily in the key of "G major")
Purple = "Minor Key" (for example a "D" whistle will also play easily in the key of "E minor")
 

The upper octave of each whistle is fingered the same as the lower octave
An alternate fingering may be needed for the note shown in Blue when playing it in the upper octave (try oxo xxx, or something similar)