No, it's probably not a true story. Many such names in stories are just part of the author's imagination. It's likely a fictional work designed to engage and captivate the readers.
I don't think Grizelda is based on a true story. Usually, such characters or stories are made up to entertain and capture the audience's interest through creative storytelling.
Once upon a time in the Rainbow Kingdom, True was a brave and kind - hearted girl. One day, she discovered that the magical crystals that powered the kingdom's colors were fading. True set out on an adventure to find the source of the problem. Along the way, she met various colorful creatures who helped her. She climbed the tallest rainbow mountain and found a dark cloud blocking the sun's rays that were essential for the crystals. True used her positive energy and the help of her new friends to dispel the cloud, and the Rainbow Kingdom was filled with vibrant colors again.
There is no real 'true story' in the sense of it being based on actual events. Rainbow Friends is a fictional horror game. The characters and their spooky scenarios are all creations of the game developers.