an azalea is repotted, silk at the end of February or beginning of March, or after the budding for me in 100/100 kanuma, as it is in bud, you will take advantage of the flowers and see what color it is!!!
In sweden most people agree that azaleas is best repotted right after the flowering. I dont have much experience myself. But your local environment will always determ when repotting is best done.