Was there ever an interracial date on this show?

I can't answer your question about whether or not there was ever an interracial couple on the show, but I do wonder why it matters to so many people.

It made perfect sense to me watching the old episodes, to see that the producers tried to match up people who were similar in appearance, because studies have shown that people are attracted to others who are similar to them in appearance, typically. Of course this isn't always the case, but more often than not, it is. And the problem is, today's generation is so easily offended, that something which probably didn't even register on somebody's radar back in the day that the show was made suddenly seems like a problem – when the fact is, it wasn't, and nor should it be thought of that way today.

Anyhow, regarding your comment that the casting seemed lopsided because of 75% of the contestants being white and only about a quarter being black, with other minorities very very rarely represented, it's not lopsided and all, considering the census breakdown of population in the United States. In fact, the percentages you gave actually over represent the black population, so it seems like the show was making an effort to be more inclusive than actually necessary to reflect the true population of the country.

Here is the official census breakdown for 2015/2016 (and bear in mind that the discrepancies between the racial groups would've been even wider back in the 1980s and 90s):

The official racial breakdown of the country, according to the U.S. Census:

Race and Hispanic Origin

White alone, percent, July 1, 2015, (V2015) (a)
77.1%
i
White alone, percent, April 1, 2010 (a)
72.4%
i
Black or African American alone, percent, July 1, 2015, (V2015) (a)
13.3%
i
Black or African American alone, percent, April 1, 2010 (a)
12.6%
i
American Indian and Alaska Native alone, percent, July 1, 2015, (V2015) (a)
1.2%
i
American Indian and Alaska Native alone, percent, April 1, 2010 (a)
0.9%
i
Asian alone, percent, July 1, 2015, (V2015) (a)
5.6%
i
Asian alone, percent, April 1, 2010 (a)
4.8%
i
Native Hawaiian and Other Pacific Islander alone, percent, July 1, 2015, (V2015) (a)
0.2%
i
Native Hawaiian and Other Pacific Islander alone, percent, April 1, 2010 (a)
0.2%
i
Two or More Races, percent, July 1, 2015, (V2015)
2.6%
i
Two or More Races, percent, April 1, 2010
2.9%
i
Hispanic or Latino, percent, July 1, 2015, (V2015) (b)
17.6%
i
Hispanic or Latino, percent, April 1, 2010 (b)
16.3%
i
White alone, not Hispanic or Latino, percent, July 1, 2015, (V2015)
61.6%
i
White alone, not Hispanic or Latino, percent, April 1, 2010
63.7%

SOURCE: https://www.census.gov/quickfacts/table/PST045215/00

Based on these numbers, it's reasonable to conclude that there has actually been a recent overrepresentation of people of color on TV and movies – probably pushed for political reasons. Because if you consider the small percentage of these people, compared to the even smaller percentage of those people in the entertainment industry, you start to understand why it is the way it is.