[Andrey_BY]

Maya, you are right - red colored tomato varieties had been dominant in USSR times even in amateur gardens.
Yellow or pink tomato varieties were very rare even in 1980s and there was no opportunity to buy seeds of such varieties in any shops before early 1990s.
Amateur gardeners from the Central part of USSR have been trading seeds by post within Soviet Union including South of Russian Soviet Republic, Ukrainian Republic, Uzbekistan, Tadjikistan and some other Southern Republics or seed exchange with neighboors near your dacha.
There were many amateur seed breeders since 1970s since Soviet people get more dachas outside major cities and small towns.

There were some other places to get more seeds:
1. From collective farms (kolkhoz) where they sometimes tested new varieties and kolkhoz staff usually took some seeds to grow at their dachas.
2. From VIR Institute staff where there has been a huge seed collection from the whole world and they still maintain it in 2018.
3. From other Soviet agricultural Institutes and Stations which took part in seed exchange within Warsaw Pact countries.
4. From Soviet militarymen families lived in East Germany (like our family), Czechoslovakia, Hungary, Poland, Cuba, some African coutries and some other countries with military bases and staff.

As for black tomato varieties there was a Chyornyi Prince (=Black Prince) which became popular in the main Central part of Soviet Union and then CIS since 1980s everywhere and then other black tomato varieties had became popular. But I have no info about Soviet South including Krim, Kuban and all -Stans.