Certain areas of the yellow section of the texture for the weathered lit copper bulb look like they contain one shade, but instead contain 2-3 similar shades. Since this only happens to certain shades and not others, and only occurs on this block, I am guessing that it has to do with a mistake with lossless compression or something similar. Attached is an image that lays out the various yellow shades in the texture, with the ones on the top being more common.
This is an issue as there are people that will likely be editing this texture for resource packs, and these extra shades existing can hamper with or create trouble with manipulating this texture.
Can confirm