If you burn anything for example - cardboard, paper, or plastic it becomes black but the sun is burning all the time so, why is it yellowish-golden?

The sun is yellowish-golden even if is burning all the time :

• Burning paper is considered a chemical process that involves an exothermic reaction.
• Paper is burned with the oxygen from the air containing carbon and hydrogen and thus after burning it turns to solid ashes and smokes.
• The sun shines in the light of the cycle called atomic combination which is due to nuclear fusion.
• Here in this process, one proton crushes into another proton and delivers some energy which produces a yellowish shading.

Hence, even if the sun is burning all the time it is always yellowish-golden.