Nested gradients break colors

[AlessioGr]

<gradient:#1985ff:#2bc7ff>Outer <GRAY>gray</GRAY></gradient>

Works fine, right? Now, adding an inner gradient will break the gray color:
<gradient:#1985ff:#2bc7ff>Outer <gradient:#00fffb:#00ffc3>inner</gradient> <GRAY>gray</GRAY></gradient>

You can reproduce it here: https://webui.adventure.kyori.net/

Weirdly, replacing <GRAY>gray</GRAY> with <GRAY><GRAY><GRAY>gray</GRAY> will make it work. Furthermore, once I replace any of the gradients with a solid color, it will work as well.

[AlessioGr]

@zml2008 Might need to be re-opened. I'm still getting the issue on 4.10.0-SNAPSHOT with strings like <gradient:white:blue>A <gradient:yellow:black>B <WHITE>C