What items in life are red squares?

Red things in life: tomatoes, pitaya, couplets, national flags, red ink, red wine, Chinese knots and roses.

Red: the color at the end of the long wave in the visible spectrum, with a wavelength of about 625 to 740 nanometers. It is one of the three primary colors of light and also a psychological primary color.

Red represents auspiciousness, jubilation, enthusiasm, unrestrained, passion, fighting spirit, revolution and so on.