weapons with yellow text?

[Forge]

Even I find the quide that Kefka linked to confusing in response to answering this question, so I'll answer the specifics.

Firstly, all of the items with CAPITAL LETTERS are 'rares' to some extent. The Merges will have CAPITAL GREEN TEXT, and the ?SPECIAL WEAPONs will have CAPITAL BLUE TEXT until tekked, when the text will become YELLOW CAPITALS. S-Ranks have RED CAPITAL TEXT.

Items with at least nine stars have yellow text, whether or not they are rare. The Yellow Normal Text that you are likely to see are originally ???? weapons whose base form has five stars (Calibur, Vulcan, Arms, etc.) When given the highest powered form of the special abililty (Beserk, Burning, Blizzard, Kings, etc.) the item gains an additional four stars. Therefore, a Burning Gladius will have eight stars and white or green text.

For weapons below nine stars, the colour of the text is dependant upon Photon Efficiency. If there are any percents (positive or negative) then it'll have green text. This is especially frustrating on DC after GC when most of the green texted weapons have negative percents.

I could also explain guard items if you'd like, including mags.