The Hue login webpage limits passwords to 30 characters. This is a problem for users with passwords longer than 30 characters – specifically when using a device such as a Yubico Yubikey to generate two-factor passwords, which can grow to ~50 characters.
I think the line that needs to be changed is:
<input id="id_password" type="password" class="input-large" name="password" maxlength="30" />
The 30 should be something larger.
I'm not sure if any changes on the backend would need to be made as well, or if Hue limits the size of the password internally somehow.