Sign colors do not work properly

I recently discovered the ability to alter colors of sign text using "§". I tried this out on the first line, changing the text to grey. I proceeded to press enter after writing the first line, and the text was still grey as I typed. When I exited the sign, however, only the first line was in grey text. Despite the fact that the text appeared grey as I typed in each line, if I did not enter the code in each respective line that line would not change color. Either the first code in line one should affect the entire sign or the color should become black again when I press enter while typing in a sign. This makes is currently very misleading.