Adjective use

I am trying to return to my study of Japanese and I just recently joined because I had some questions about adjectives.

This tripped me up.
オレンジジュス - orenjijusu
I thought that orange being a color was an adjective, and that adjectives where had an adjective marker like na after them.
So can I not say?
しろなまる - shiro na maru
Are both right? Is one right and the other wrong? I am really confused

"Orange" is also a fruit...

オレンジジュース refers to "the juice from an orange" and doesn't mean "a juice which is the color orange"....just like in English.

しろなまる is not correct, because the adjective form of "white" is しろい.

The color orange is オレンジ色 (orenji iro).

There are two classes or groups of adjectives in Japanese: い adjectives and な adjectives. You need to review them again.

What did you use before to study Japanese? What are you using now? How long have you been away from studying?