Once your sound has been created at the vocal cords, it will move up in the spaces in your throat, mouth, and head. As the sound resonates through these spaces, it changes tone quality depending on the proportion of each cavity.
There are vocal tonality exercises that you can practice that will "teach" you to vary these proportions, so you can change your tone quality as you desire.
It's like an artist having access to a full palette of colors...
As a singer, you can learn to sing in a full range of different vocal colors.
You can learn to balance your vocal resonance once again, through good vocal tonality exercises. Once you learn to do this, your voice will be rich in tone quality, and balanced through your entire range.