Reading an old post that I didn't get around to publishing before, a new droplet has formed where the last one dried.
The gist of the first idea was to actively colour the letters on a page, to employ the brain's colour-recognition to improve spelling and reading ability. The flaw I found in reading further was that dyslexia and synaesthesia (seeing certain letters as coloured) are related.
In particular, this quote stuck out:
"My daughter, aged 11 is dyslexic and has grapheme-colour synesthesia. The colors negatively affect her ability to read and to spell, since some of the letters have the same color. E and U are both green, for example. She also tends to group the colors and hence inserts letters into words because she thinks their colors “go together”." - Mary G.
Mary G's daughter seems to see spelling as a series of colours, and can thus happily swap E and U. However, there are likely to be other aspects of shape that affect the colour. For example, what colour is a spikier E, or a U with a wiggle in it? Intuitively, the changed shape would affect the letter's perceived colour, which might help Mary G's daughter. If an entire font was created based on a fairly standard font, in which certain letters had particular changes made, that girl and others like her might find reading easier, and might make recognising incorrect spellings easier too.
Inevitably, as this is based on intuition, I'm probably wrong. If the girl perceives all Es and all Us as the same colour, regardless of font or handwritten, this won't help.
One alternative might be to attach simple musical notes to the different letters, making sure they harmonise, but that problem groups like E and U do not sound similar. As she types, the flow of notes will be recognisably right or wrong for a given spelling.
Admittedly, the girl could just rely on Word to correct her spelling all her life. She will also need to learn to spell when writing, and paper can't do customised sound effects.
But she could do a spelling bee with a little humming.