Where has this been mentioned? I have not heard of this.
Anyways, judging from the fact that the mask was yellow in both Jaller sets back in the golden years, and that Lhikan is described as yellow in the books, he might actually be yellow, not gold in story... But I don't really know. Does it really matter? Not really. Was he a Toa Hagah? No. Lhikan's Toa career wasn't actually that long, iirc, it was less than 7 000 years, and most if not all Toa Hagah teams are older than that. Add to it, he spent most of his time as a Toa in Metru Nui, there would have been no time for him to make a large enough name for himself to become a Hagah. I do believe Greg said he had the same mask, not as in a Hau, but the Hau when he was a Matoran, and presumably; though this shouldn't be taken for granted; he would have had the same colorscheme. (The Inika did not however, which is why this shouldn't be taken for granted, however the Inika were also transformed via unorthodox methods.)
Note however; the Toa Hagah rebellion took place after Nidhiki being mutated, so I guess he could have been a Toa Hagah?... Though that'd be near impossible, and extremely doubtful. Plus I'm pretty sure Greg would say no...
The Toa Hagah armor is not really special other than they were gifted new armor, weapons and masks when they became Hagah. These were made from precious metals. It should be noted here that the two things making them special is the rare and/or valuable material used, and the fact that they were gifts. The color is not what's important. You can have a gold color without actual gold, for example, there's brass. It's just a color.
Conclusion: Whether he had gold or yellow armor is up to interpretation. Did it denote anything special like the Hagah or Nuva armor? No.