Q. Shalom,
In an online search, this site came up, but I can’t find a way here to search for the relevant post…
I was asked if there’s a mekor to say that the Gemara in Horios re olives, is only referring to black (ie ripened) olives and not green (unripened) ones.
Do you have such a mekor?
My question (above) is as below regarding olives. Any mekor to be mechalek between green and black?
A. Olives naturally turn black as they ripen. When unripe they are green. As they ripen they get reddish, then purplish and finally black. “Ripe Black Olives” in a can are actually olives which are neither black nor ripe when they are picked.  They are picked very green and then cured using dilute brine and lye solutions. (oliveoilsource.com)
Similarly, the Encyclopedia for Kashruth Hamazon (p. 142) explains that olives are usually green at the end of their growth. Black olives are green ones that darkened by a salting process at the manufacturing plant. He adds that some types of olives may become black by leaving them an extended time on the tree. He also mentions (P.141) black olives in regards to the inherent difficulty in checking them for worms due to their color. However, he maintains that after the fact they are permitted, since the majority are not usually affected.
Zecher Assa (a sefer dedicated to the prevention of shickcha or the forgetting Torah, with an emphasis on dietary issues), amply explains what the Talmud (Horios 13b) teaches in regards to olives promoting forgetfulness. He quotes (on p. 318) the opinion of Avraham Ezkor that only black olive cause shickcha, but promptly dismisses it and opines, reflecting many Poskim, that it applies to all olives. He also mentions a tradition in some places not to eat black olives during the month of Nisan, as the month is dedicated to the memories and recollections of our Exodus from Mitzraim. (He mentions, that on his location the majority of the olives were black).
Poskim dedicated to Kashrus, mention black olives conserves, in regards to their probability of containing tartaric or lactic acid (Orchos Habais p. 29 Taasias Hamazon p. 32).
Beis Nachem-ya (p. 253), Chaim Vachesed (8: 5) mention the minhag to serve black olives at the “seudas habraah” meal after a funeral. Maasseh Nissim (O.H. 42) quotes a tradition not to eat black olives on Shabbos, as it may be the food of avelim.
Horav Shlomo Miller Shlit’a pointed out that on Rosh Hashono some Poskim mention not to recite shecheyanu or eat black olives. (Shesh Moshzor O.H. 10 p.52).
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a