There are free alternatives for sure. Not worth to pay for. Any RGB KB and mouse already have S/W which will change colors in spectrum. And if yellow can be gold – maybe nice but not worth the $$ to pay for .
However there was and still is old app called Bukva Zu
I use the program SNOOP.EXE (if the text is typed in the wrong layout)
SHA-256 176F8972A123443A559AF4C93B671B292894A003887FF41093AF455E94904ED8
system for the transliteration: ISO_9 en.wikipedia.org/wiki/ISO_9 and +26 languages
Just in case, there is a letter in the Latin alphabet: Ë, ë (U+00CB, U+00EB) en.wikipedia.org/wiki/Ë
(not to be confused with the letter jo, yo (U+0401, U+0451))