In article . com,
wrote:

Lets be historic. Margarine was introduced as a butter replacement
during WWII. It was originally made from vegetable oils not animal fat
which was also rationed. It came in a one pound plastic wrapped block
with a small capsule of coloring in it. You broke the capsule and
kneaded the block until you got the yellow color. This coloring method
was insisted on by the dairy industry as they did not want a
competition for butter developed, but the genie was out f the bag
anyway and margarine became a staple alternative to butter.

http://nativechefs.com


For some brands, the coloring came as a powder in a small glassine
packet. You sprinkled the color over the nearly-room temperature "oleo"
and then stirred with a big spoon until your arms got tired (as I
remember...:-)

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