Scribus+Notes

RGB Colour Scheme Why do pictures use RED GREEN BLUE and not the 3 primary colours RED YELLOW BLUE?

As kids we were taught in art class that the primary colors were red, blue, and yellow. By mixing these primary colors, we were told, we could come up with any color of the rainbow. Now that we are older and in the age of video, we have been told that color TV monitors use red, blue, and green as primary colors. The obvious questions are, how do you mix red, green, and blue to get yellow?

A spinning wheel with a red, green, and blue color wheel attached to the tip will merge into a sort of light gray. It turns out there are two ways of creating colors--the additive method and the subtractive method. When using the additive method, the primary colors are red, blue, and green. The more additive primaries you add, the lighter the resultant color. Mix all three and you get white.

The subtractive primaries are red, blue, and yellow--to be exact, magenta, cyan (light blue), and yellow. These are the colors that, together with black, are used in color printing. The more subtractive primaries you mix, the darker the color. Mix all three and you get black (OK, brown, but with kindergarten paints you can't expect miracles). As a general proposition, additive primaries involve adding more LIGHT (as in a color TV), while subtractive primaries involve mixing more PIGMENT (as in paints and crayons).

Additive colors are easy to demonstrate on a color computer monitor equipped with a color-control program. Just so happens I have one right here. How do we make yellow? By adding full-strength red and full-strength green. Adding two-thirds strength blue gives us a lighter (not darker) yellow. Full-strength blue, red, and green produce bright white. This is a counterintuitive result if you learned your color-mixing skills in kindergarten. But we know that white light can be broken into all the colors of the rainbow. So we shouldn't be surprised to learn the process also works in reverse--i.e, the colors of the rainbow can be combined to make white. Besides, it only stands to reason that the more light you shed on something, the brighter (that is, closer to white) it gets.

The additive color- mixing chart as follows: Green + red = yellow Green + blue = cyan (light blue) Red + blue = magenta Red + blue + green = white

Subtractive colors, as the name suggests, work by subtracting certain colors from white light and reflecting the rest, like so: Yellow pigment absorbs blue--reflects red, green Cyan absorbs red--reflects green, blue Magenta absorbs green--reflects red, blue Blue absorbs red, green--reflects blue Red absorbs blue, green--reflects red Green absorbs blue, red--reflects green

If white light strikes yellow paint, the paint absorbs blue and reflects red and green. Then the additive principle takes over--red and green combine to make yellow. Now mix cyan (light blue) and yellow paint. The cyan pigment absorbs red light; the yellow pigment absorbs blue light. What's left is green, the color you see. How do you know whether it's additives or subtractives you're dealing with? Ain't easy. Spotlights, TV electron guns, and spinning color discs are additive; pigments, filters, and stationary color discs are subtractive. Confused? Who isn't these days? But perhaps at least you understand the apparent paradox of a TV making light colors from dark ones.

=PRINTER COLOURS=

When saving to a PDF change the colours to SPOT. SPOT colours tells the printer to print in a colour close to the ones on screen. Below is an example of SPOT colours common printers use:



If you want to know more about colours view...
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