Gender equality is when people of all genders have equal rights, responsibilities and opportunities. Everyone is affected by gender inequality – women, men, trans and gender diverse people, children and families. It impacts people of all ages and backgrounds.

But here as you said the college rejected your admission because of your gender is totally wrong. Each and every person has the right to education and no institution shouldn’t snatch it from anyone. And a college isn’t allowed to deny any applicant from admission on the basis of gender if there are seats available.

Gender Equality was made part of international human rights law by the Universal Declaration of Human Rights, which was adopted by the UN General Assembly on 10 December 1948.

Right to Equality (Articles 14 – 18) The right to equality provides for the equal treatment of everyone before the law, prevents discrimination on various grounds, treats everybody as equals in matters of public employment, and abolishes untouchability, and titles (such as Sir, Rai Bahadur, etc.)

Article 15 secures the citizens from every sort of discrimination by the State, on the grounds of religion, race, caste, sex or place of birth or any of them. However, this Article does not prevent the State from making any special provisions for women or children.
So, You can file a case against that college on the basis of violation of the right to equality.