Back in the day, when “oleo” came in a white color, my mother said her family mixed it with turmeric to get the normal “butter” color.
Turmeric, a great anti-inflammatory spice, also helps rheumatoid arthritis (personal experience).
At the time, it was unlawful in many places to sell oleomargarine already colored yellow. It often came with a little packet of coloring instead.
As you might guess, this was the doing of the dairy lobby.
ps.: Another powerful yellow food colorant is beta carotene in small concentrations.
So that is what that package of yellow stuff was! My mother let me mix it into the white margerine. I thought I was cooking. ha!