That was true but due to copy rights Tomino had to change the Gundam`s color. There`s another SW item in the first Gundam movie when the first time Amuro uses THE TRACKING or THE TARGETING SYSTEM in the RX-78-2 !
The way I heard it, they colorized the Gundam because the people funding the show wanted bright primary colors, because a solid white toy would look boring on the shelf.
Yup.
I you read the Gundam novels the Gundam is white until Amuro gets the second version G3 which is Grey.
Tomino wanted it white but Bandai wanted more bright colors to sell more toys.