Colored Names Prevent Names

So I wanted ti see if I could join a game with a colored text. I changed my name to light green and tried to join my sister's world. It said "Invalid Name" so I went back to change my name back to a regular no-colored name. When I deleted it all, the blinking margin disappeared. Then I tried to put my Minecraft name back, but when I typed on my keyboard, nothing was being typed. This means that i cant join anyone's world because it says "Invalid name". Please, find a way so I can pit my name back without rebting and long restoring that I don't know how to do.