Assuming your employer has at least 15 employees, it would be illegal for it to discriminate against you on the basis of your race. You would have to show that you are qualified for the promotion you are seeking, but that employer consistently promotes less qualified junior employees of a different race. The employer would then be require to show that it had a legitimate non-discriminatory reason to make the decisions that it made. it is the same thing with the OT opportunities, you would have to show that you were qualified and available but that the employer consistently gave the opportunities to persons of another race.
These are complicated and difficult cases to bring, You would be benefitted by a consultation with an employment lawyer, who could help you sort out whether or not you had a case that was likely to succeed. www.nela-ga.org is a good source for employment lawyers in Georgia. Good luck.