"The garage is a big and cold garage."
Translation:اَلْكَراج كَراج كَبير وَبارِد.
İ didn't really get what you mean here... But maybe the following may help:
The first word الكراج is the first mobtadaa "مبتدأ"
The second كراج word is also a mobtadaa "مبتدأ" but a second one
The third abd fourth words كبير / بارد are adjectives for the garage but thier role in the sentence is considered to be khabar / خبر for the word كراج (the second one)
And the sentence كراج كبير و as a whole is considered to be the kahbar for the first mobtadaa "الكراج" ....
Because the two adjectives are not mutually exclusive and they don't specify each other, you can write them in either order. If however, the adjectives were describing one another, the order would matter. For example, "a light blue jacket" the word "light" is describing the word "blue", so you cannot say "blue light jacket" but if the jacket was light, as in lightweight, you could say "a light, blue jacket" or "a blue, light jacket" and either would be correct.