When children learn the alphabet, they usually learn the names of letters. To begin reading, they also need to discover the sounds those letters represent inside words.
That distinction is important.
A letter may be pronounced differently in different contexts, while a speech sound may sometimes be represented by different spellings.
Reading is therefore more than simply knowing the alphabet.
Colored Letters makes sound information more visible by adding colour as a supporting cue.
The colour does not replace the letter. It provides additional support while the child practises the connection between written and spoken language.