What is the ruling on prayer and fasting after the cessation of clear bleeding and the change in the color of the fluid to light beige following the miscarriage, knowing that the bleeding period exceeded forty days?

If the pregnancy did not show the formation of a human being, then the blood is blood of corruption (fasad), and your ruling is that of a woman experiencing irregular bleeding (mustahadah). You must make up for the prayers you missed.

However, if the miscarried fetus showed the formation of a human being, then the blood is blood of postnatal bleeding (nifas (definition)), and its maximum duration is forty days. What you see after forty days does not carry the ruling of nifas, unless it coincides with your customary menstrual period, in which case it is menstruation (hayd). It is more precautionary to make up for the prayers you missed.