But it depends on materials; for example, if clay brick is pink, it calls underburnt temperature is 700 degrees -900 degrees, paste red is called overdo temperature 1350 degrees -1390 degree, if the color turns heavier, it will be deformation. there are many reasons for refractory bricks sintering
Dark red? Bright red? Orange red? 400,1100 or 1500 probably
If the raw materials are different, then the redness is different under different temperatures.