I grew up and lived in the US for 10 years (I’m a US citizen) but I’ve been living in Egypt for the past 8 years. Am I considered an international student or US citizen when I’m applying to colleges?
There is not advantage to be an international student. Also, living in Egypt does not mean you are a citizen there. The question is do you have a foreign citizenship.
You are a US citizen for admission.
Unless you claim some other citizenship besides American , you’ll be regarded as a US citizen with foreign residency. As a US citizen, you are eligible for US federal financial aid if you meet income requirements.
You pose this question like you have a choice in the matter. 
Each college will put you into whichever bucket it sees fit (most likely as US citizen living abroad). It would be much better for you to focus on things which you can actually impact. Good luck!
“Us citizen living abroad” is one of the best categories to be in (you get the “international exposure” advantage, but none of the drawbacks, especially for financial aid. 
Anyway, universities will decide.
@seniormess - Contact each of the colleges and universities on your list, tell them that you are a US citizen living abroad, and ask them which application you should use, and what materials you need to provide them. Do not be surprised if each place asks for something different. That is OK. Send whatever A wants to A, and whatever B wants to B.
If you are attending an international school that sends many students to the US each year, your own guidance counselor should be able to help you through this process. If your school rarely sends students to the US, contact the closest AMIDEAST office. http://www.amideast.org/ The counselors there will be able to help you out.
Yeah I have a dual citizenship
Apply with your American citizenship. Indicate you’re a dual citizen of course, but apply as an American citizen, since you’re one!
(Plus, applying as a non citizen makes things ten to a hundred times harder for students so don’t purposely do this.)