To do this tutorial you need to know what a semitone is.
Two notes are a tone apart if they’re 2 semitones apart. So C and D are a tone apart because C to C# is a semitone and C# to D is a semitone.
A tone is always two notes of the same colour next to each other, unless it crosses a
Play lots of tones on the piano, including ones that cross boundary lines.