There has been much confusion about color over the years, and perhaps the biggest confusion has been the differences between mixing colored light and mixiing colored inks or paints.
When mixing light, it is called additive color mixing. In the photo, blue, green, and red light are mixed. Where they all intersect, white is formed. In other words, mixing Blue, Green, and Red light yields white light. This is how color is viewed on your computer monitor. Red, Green, and Blue lights are combined to produce colors.
When mixing pigmented ink or paint, it is called subtractive color mixing. By mixing Blue, Red, and Yellow pigments together you get Black. This is how color is viewed when you look at a Pantone book.