This arrangement of black and white keys is only one of two possible arrangements. The other arrangement (known as the 'transposed' position) places C on the second row of keys as follows:

('Transposed' position)

However, the 'default' position is used as the 'fixed' layout on keyboards, for reasons that will become clear:

 

('Default' position)

A simple two-position switch (or mechanism) to transpose the pitch of the keys upwards by one semitone enables the keyboard to play both arrangements[1][2]. This option is extremely useful to those who play the instrument as relative (moveable) positions rather than by fixed notes[2][6], and is useful should it be more comfortable to play certain chords or scales from a lower key rather than a raised key, and vice-versa. 

The only problem with this feature is that the colour of the keys can only correspond to one arrangement correctly. However, there are several solutions to this problem for electronic musical instruments; these involve changing the colour of certain keys on the instrument.

One solution involves making the ‘black’ keys a different colour such as red, blue, or green, the others being left white. In this embodiment, the keys representing C and F in the default position are made of a white material that is transparent to a coloured LED light contained within them. This material should be of a substance that best scatters the light most evenly across the surface of the key. When the keyboard is in default position, the LED lights are off, resulting in the arrangement shown on the prototype below, with the white keys representing C, D, E, F, G, A, and B, and the red keys representing C#, D#, F#, G#, and A#:

However, when the keyboard is switched to the transposed position, the red lights are turned on to match the other red keys so that they now represent C, D, E, F, G, A, and B, while the five white keys now represent C#, D#, F#, G#, and A# (similar to a harpsichord or early piano):

Conveniently, the keys with LEDs retain their outward surface texture that enables these keys to be identifiable by touch alone. In a darkened environment, these keys would appear as follows in the transposed position:

The chosen colour of fixed keys should be of a quality easily produced by an LED light, while the permanently coloured keys should be made to best match this quality of this light.

[3][3] If the note C is based on the lowest row of keys, then it is said to be in the default position, otherwise it is said to be in the transposed position.

[4][6] That is, a musician can learn a chord progression from one key, and then be able to play it in any other key in the same way. This is also useful when performing with musicians who are limited to (or have a preference for) certain keys; it can also be used with ‘moveable’ bilinear notation.