The first Bitcoin logo satoshi made is gold colour with some shades like a actual physical coin.
Then bitboy create another design of Bitcoin logo with flat orange colour, it's more simple and readable than the old one. However the orange colour isn't really orange, it's more like
golden orange. Probably the colour are not contrast and eye catching, so he change to orange.
Meaning of orange colour
Orange is associated with meanings of joy, warmth, heat, sunshine, enthusiasm, creativity, success, encouragement, change, determination, health, stimulation, happiness, fun, enjoyment, balance, sexuality, freedom, expression, and fascination.
https://www.bourncreative.com/meaning-of-the-color-orange/https://www.coindesk.com/about-that-orange-b-the-history-of-bitcoins-logos 
