"He was later relocated to Metru Nui by the Order of Mata Nui during the Time Slip, disguised as a Ta-Matoran, though due to his lackluster amount of control, his disguise was a poor one."
According to the same source, orange was a typical Kanohi color for Onu-Matoran, as was tan.
I wouldn't get to stressed over the Makuta not being these ancient and knowledgeable beings, that was never really their purpose, and as such there's a lot of things older than them in the MU.
What there is to be in awe of the Makuta for is their ingenuity. It was their curiosity and inventiveness that lead to the discovery of Mata Nui's true nature, and through that same tenacity the virus that brought him down was crafted. It was the same creativity that gave Teridax the plan to use his essence to infect Matoran, and the Karda-Nui Makuta to use Shadow Matoran to augment their senses. Old and wise, maybe not. Intelligent, resourceful, and relentless, definitely.