Believe it or not but I have something new to add on the very long post from way ago.
As some of you would know I used to restore these badges before the new repro ones were made.
The process goes like this;
1. clean badge using caustic soda
2. wash thoroughly and polish the plastic for best results
3. Paint with opaque enamel in required colour
4. Have a vacuum metaliser company apply the finish to get the chrome backing
5. Paint the back to protect the metalising.
Usually the badges come out with a silver (or chrome) lion as you would expect when chrome is applied to clear plastic, but some come out with gold lions
.
My definitive answer is the following - a different type of plastic was used on some badges which creates a gold colour when the metalising process is done. Whether the 2 different suppliers used different plastics, or 1 supplier used 2 different types of plastic I don't know.
Of the colours - I have seen the shield in silver, gold, blue, green, brown & purple. My 3 tone green FC had a badge with a green shield in it. There may have been some attempt by GMH with the late 59 cars to experiment with coloured horn buttons since this was done in the FB model in the stars.
Ken