I don't understand the blackbody concept here.
You don't have to ( and most people don't, apart from a handful of theoretical physicists maybe).
When you heat a bar of iron, it changes color, depending on it's temperature. You can look up the blackbody temperature of the sun, for instance and plug that in to get a theoretically correct color of the sun.
Fun fact: when increasing the temperature, the visible color goes from red to blue, blue being the hottest (towards 10,000K, hotter than the sun) and red the 'coldest' (maybe 1000K).
Artists usually think of blue as cold and orange/red as warm.
