Some were, some were not. If you look through any collection of paintings from ancient Egypt you will see a variety of skin tones represented. Red-brown seems to be the most common that I have observed, but you will find people portrayed in colors ranging from light skinned almost Caucasian/northern european/pink all the way to what is most certainly black African. Most commonly would be those from Kush, which is now Sudan.
The kings of the 25th dynasty were from Kush so they most likely were.
Something to remember when asking this question is that the "Egyptian" you're probably thinking of refers to 2500 years of a culture that interacted regularly with both its neighbors in the Levant and Arabia, those to its south in modern Sudan, and eventually those across the sea in Greece. So as barrett51bmg mentioned, many people from the south considered themselves Egyptian, and some even became rulers. Yet someone like the ever-popular Cleopatra and her Ptolemaic predecessors would have had a significant amount of Greek ancestry.
One thing we can say for sure is that whoever was producing the majority of Egyptain art did see a distinct divide between Egyptians and foreigners. Those from the east have long, full bears and caps, while those from the south often had a unique hairstyle.