I think someone had posted about this earlier, and I remember Sirrion asking for examples, but I cannot find it now so here is another post about it. I think the mage towers are a bit confused.
The Palanthas towers are colored red, black, white and that seems to work fine. A neutral transmuter can enter the red tower:
<378/378hp 619/619mana 213/232mv 120935tnl | NSW> Before a small tower engraved with a red moon
You are standing in front of a tower that has been built from some
strange red stone. An arcane symbol of Nuitari's red moon adorns the
entrance and magical firestones light up the room. You can head back east
to Arcanus lane.
[Exits: north east]
A powerful iron golem stands vigilant guard over the guild.
<378/378hp 619/619mana 212/232mv 120935tnl | NE> n
Inside the tower of red-robes
You stand within the tower of the red-robes of Palanthas. It is here that
the mages practice and teach their powerful magics. The tower goes up to
the guild room and south outside.
[Exits: south up]
( 6) A tankard of frothing ale is here.
A perfectly made rug of felt appears very comfortable.
Thror the male gnome is sleeping on an elegant woven rug.
A guard is here walking the battlements.
<378/378hp 619/619mana 211/232mv 120935tnl | SU> u
the Red-robe's laboratory
You are within the guild room of the red-robes, a mystical room
protected by strange arcane runes and designed to be impregnable against
enemy summons and gates. You can head back down to the floor of the
tower.
[Exits: down]
(12) A delicious magic mushroom is here.
A guard is here walking the battlements.
A tall knight dressed in warm clothes eyes you carefully as he passes.
(White Aura) Your guildmaster stands here.
In New Thalos, the same neutral Transmuter cannot enter either red or white tower:
[Exits: west up]
An Elite Royal Guard stands here smiling happily.
A guard stands here, protecting the innocent.
A white-robed mage is here watching the guild entrance.
<378/378hp 619/619mana 231/232mv 120935tnl | WU> u
A White-robe guild guard moves to block the way up.
A White-robe guild guard says, 'You aren't allowed in there.'
<378/378hp 619/619mana 231/232mv 120935tnl | WU> w
The Mage's Courtyard
You enter a small tiled courtyard with a small fountain in the middle.
Around the sides are four wrought iron benches with cushions where the
mages of the land sit and exchange ideas. To the west stands a two-story
red tower where the leader of the mage's guild performs his experiments,
and to the east is a similar white tower.
[Exits: east south west]
A guard stands here, protecting the innocent.
A tourist stands here looking lost.
<378/378hp 619/619mana 230/232mv 120935tnl | ESW> w
Base of the Tower
You walk into a cold room whose only feature is an old wooden staircase
spirling up along the wall to a higher level. Up these stairs, you are
told, lies the old mage who may be able to help you advance in your
studies.
[Exits: east up]
A red-robed mage is here watching the guild entrance.
<378/378hp 619/619mana 229/232mv 120935tnl | EU> u
A Red-robed guild guard moves to block the way up.
A Red-robed guild guard says, 'You aren't allowed in there.'
And in Caergoth, the towers are reversed for the same neutral transmuter where the red-robed transmuter enters the tower guarded by the white robe (because of the transmuter class):
<378/378hp 619/619mana 178/232mv 120935tnl | SU> look
Entrance to the invoker's guild
At the bottom of this tower of red-stained marble are inscribed
runes of protection for those who practice and master their spells
above. There is a red circle above the entrance to the tower,
symbolic of Lunitari, goddess of the magi of the red robes. To
the south is the courtyard.
[Exits: south up]
A large minotaur wanders about the town while his ship is in port.
A large minotaur wanders about the town while his ship is in port.
A red-robed mage is here watching the guild entrance.
<378/378hp 619/619mana 178/232mv 120935tnl | SU> u
A Red-robed guild guard moves to block the way up.
A Red-robed guild guard says, 'You aren't allowed in there.'
<378/378hp 619/619mana 178/232mv 120935tnl | SU> s
a courtyard between the towers
You stand between a red tower and a white one; where the magi of
the town practice their spells and learn new ones from the masters
living there. It's a pleasant-looking courtyard, with some flowers
and grass, and a gargoyle fountain set into the stone of the eastern
wall. The red tower of the invokers stands to the north, while the
white one of the transmuters is to the south. To the east you see a
break in the city walls allowing you to continue down the cobblestone
path and into the neighboring plains.
[Exits: north east south west]
A stone fountain shaped like a gargoyle sprays out water.
<378/378hp 619/619mana 177/232mv 120935tnl | NESW> s
Entrance to the transmuter's guild
At the bottom of this tower of white marble are inscribed runes of
protection for those who practice and master their spells above.
There is also a white disk above the entrance to the tower, symbol
of Solinari, god of white-robed mages. Back north is the courtyard
between the two towers.
[Exits: north up]
A white-robed mage is here watching the guild entrance.
<378/378hp 619/619mana 176/232mv 120935tnl | NU> u
The transmuter guild
This tower is actually the humble home of a powerful mage, who is
teaching students of transmutation what he knows out of the kindness
of his heart. There are a few round windows looking out of the white
tower, and a small bed is under one of them. Mystic runes of magical
protection are carved into the walls, glowing softly.
[Exits: down]
(Charmed) A cute kitten is sleeping here.
(White Aura) Your guildmaster stands in the tower, ready to teach you.
I didnt check the guilds in Nethosak, but I think that was discussed in another post on here.