Cai Thiệp: Invitation/festive card , Cai Cạc: business card , Cai Thẻ - ID card
I was wondering the same thing, since "card" can mean many different things in English. I did an image search for "cái thiệp" on google.vn and it seems to mean birthday card, Christmas card, happy women's day card, wedding invitation card etc. Basically cards to celebrate special days. https://www.google.com.vn/search?q=c%C3%A1i+thi%E1%BB%87p&biw=1366&bih=643&source=lnms&tbm=isch&sa=X&ved=0ahUKEwipid-iy63NAhVmKcAKHYDrCMMQ_AUIBygC#imgrc=_
this sentence is problematic. It say my card has a red color. meaning it could have a tiny bit of red in it. The translation in english claim the card is red, not that it has some red in it.
The answer says "my card is red" but it really should correctly be written as "my card has red color" also thiệp sounds more like an invitation rather than just plain card