I think the problem lies more with the placement of the color as it looks like it is the energy coming from him, which for someone empowered by the elemental power of ice, should not be yellow.
If we theoretically translated this color scheme to a constraction figure, it would probably resemble Takanuva more than Kopaka.
Ihu Castle (WIP) with the color schemes.
I just can't buy into the idea of yellow being the color of Kopaka's energy. If we could come up with a clever way to explain it I would probably feel a lot better about it.