90 years ago what proportion of America university students weren't white (IE whatever people at the time would consider "white" to mean)? what proportion (if any?) of Ivy League students weren't white?

90 years ago would be 1925, but I am going to use 95 years ago, 1920, because that was a census year, so it is possible to get some statistics.

The total US population in 1920 was 106 million. 95 million White, 10.5 million Black and 0.5m Other.

https://www.russellsage.org/sites/all/files/blau_ehrenberg_tables%20figures.pdf

In 1920 about 12% of African Americans graduated from high school, about 28% of European Americans.

In 1920 about 2% of African Americans graduated from college, about 7% of European Americans.

(These numbers are percentages of the age cohort that could graduate in 1920, not of the total population).

https://www.russellsage.org/sites/all/files/Fischer_Hout_Tables%20Figures.pdf

So, about 3,000 African Americans graduated from college in 1920 and about 95,000 European Americans. (Just taking % graduates as a % of total population and dividing by 70 years average life span, to get the college graduation cohort – not very precise but roughly indicative.)

The "Other" category in 1920 consisted of American Indians and South Pacific Islanders. They had just slightly lower college graduation rates than blacks so roughly 143 graduates in 1920.

To answer your question; about 3% of college graduates were non-white 95 years ago, whereas 10.4% of the population was non-white. (I know your question was about college students, rather than graduates, but I assume the percentages might be roughly the same.)

The overall numbers of male and female college graduates were almost equal in 1920. (Male graduates outnumbered female from 1930 – 1980, then female graduates began to outnumber males). (Don’t know if this was the case for Black college students in 1920?)

I don’t have statistics for what % of Ivy League students were not white in 1920. In 1900 20% of black college graduates had graduated from “white” colleges and 80% from “black” colleges, but don’t know what that was looking like in 1920.

Ivy League colleges were among the earliest colleges to enroll and graduate non-white students:

1665, The first non-white to graduate from Harvard. Charles Cheeshahteaumuck from the Wampanoag American Indians.

1828 1st African American to graduate from Dartmouth. 4th African American to graduate from any US university.

1857 1st African American to graduate from Yale.

1869 First black to earn a degree from Harvard Law School (later becomes 1st black judge in Massachusetts).