Look at the number Mod 1. When you look at a number Mod n, you just divide by n, and look at the remainder. So here you divide by 1, and the remainder is just the fractional part. The best way to do this depends on the language.
Simple paint a long horizontal black stroke on a scratch piece of paper and then once it dries paint your watercolors colors in short vertical strokes on top of it. If the paint appears to sit on top of the black stroke the paint is opaque.
Black is the darkest color, the result of the absence of or complete absorption of light. It is the opposite of white (the combined spectrum of color or light). It is an achromatic color, literally a color without color or hue. It is one of the four primary colors in the CMYK color model, along with cyan, yellow, and magenta, used in color printing to produce all the other colors. Black was one of the first colors used by artists in neolithic cave paintings.