There are no doubt many methods out there to help you and I would advise you to seek some assistance from a specialist teacher or speech pathologist. My suggestions are only based upon my own experiences and I will mention a few things that I have found useful in the past.
You mentioned associating specific sounds with colours. This is a good idea.
For example, you can colour the hard and soft sounds of some consonants differently. You can also do this for the short and long sounds of vowels.
silent letters may also be coloured in a light colour.
it might be an idea to find an International Phonetic Alphabet Chart (IPA) which contains many of the sounds of English using symbols to represent the sounds. Instead of using the chart symbols you could use a colour. For example, the short I sound in the word sit could be represented by blue and the long I sound in site could be red and so on.
Using an IPA chart is great to use as a reference point and can be referred back to by yourself or a teacher. For example, if you read the word site and pronounce the I as a short vowel (blue) then your teacher may correct you and say :> no, use a red I
You can download these charts from most websites and then use colours instead of the provided symbols.
Just google IPA
You can also use shapes to represent different sounds. For example, use squares to surround long vowels and circles to surround the short vowel sounds. You can cut out letters and shapes to use them together. You could, for example use triangles to surround consonant blends e.g. For ch as in church you could surround the c and h with a triangle each to show that they work together to make one sound .
Sometimes I have emphasized long and short sounds by drawing long letters on the page verses short letters for short vowels.
To show which parts of a word are louder and longer (=stressed) people sometimes bold the stressed part or use a colour or even draw circles above the stressed syllable.
Above all, try to use all of your senses to spell and pronounce words.
For example I once taught a student the difference between the hard and soft sounds of the letter c by using cut out letters made of foam for soft and wood for hard.