Ah, I see. Ευχαριστώ! (That especially makes sense in this case since there is no audible difference in the original French words either- "cache-col"/"cache-cols"). So, just to confirm, there is no declension at all for these types of words? Would "the color of the scarves" be "το χρώμα των κασκόλ"?
Normally, yes. No case declension at all. Colloquially, you may hear someone adding endings on the spot. I must have said one or two times των κασκολιών for example but it is not something you will find in the dictionary. It's just an on the spot greekify of foreign words that may come naturally when a native is speaking that may or may not occur.
I think there has been a mix-up of different questions and answers here. I guess Suzanne was referring to a tiles exercise, which I didn't understand while answering the question. Then Bill probably meant to reply to my bottom comment↓, because he does mention a "funny" tile, which means that there's indeed a tile including an apostrophe.
Dear GG, thanks for the responses, and sorry for my long delays. I was offline for many months. This is really a wonderful program here, just a few bugs here & there. Also at one point in the instructional documents, the Greek author misspelled "career" in English as "carreer". You might take a look at that. I didn't see this misspelling pop up, however, in any exercise. Cheers to all who make this possible!!! S.