RGB colour mode is primarily used working on graphics to be displayed on television or computer monitors (i.e. websites or video) Red, Green and Blue are the primary colours when working with Light. So how can you tell it uses RGB, look very closely at your screen to see a small pattern including Red, Green and Blue dots (RGB colours). When RGB colours are blended together equally and it creates white none of the colours present black is created. This colour is known specifically as ADDICTIVE COLOUR.
The secondary colours are Cyan, Magenta and Yellow. A simple theory is imagining sitting in a dark room with no light at all the wall in front of you will appear black. Now with three friends sitting directly behind you were to shine three lights Red, Green and blue, the three colours would appear and any overlap creates the white light.
Red and Green create Yellow light, Green and blue create Cyan and blue and Red create magenta light. But interestingly when the three colours combine together equally they then create White. This is called RGB colour mode and is why it is used on video and website design graphics.
This colour mode is used for print purposes or media, you may have heard it called the four colour process. Main colours are Cyan, Magenta, Yellow and Black. It is used when applying ink to paper or canvas. You must double check with the printer before sending artwork as some large format printers can use other colour modes for printing depending on their set-up.
If you have a graphic ready but it is in RGB mode you can convert it to CMYK, but be aware that this can make the colours very muddy (Subtractive colour), it is always best to start out using the colour mode you are going to use rather than converting the graphics.
This is why a printers proof is important to get a feel of how the piece will print, too many clients sign off design from screens and when they receive the print ask questions about why the colour looks different. So be sure to get artwork signed off from a printed version rather screen. The difference between RGB and CMYK is how it uses light, CMYK does not give off light of its own, and it simply reflects light from additional sources. In CMYK white is created by absence of colour and the black created by combining the three main colours.
Cyan and Magenta create Blue, Magenta and yellow create Red, Yellow and Cyan create Green. Black is createdby combining all colours equally; White is when no ink is present thus blank canvas or paper. If a client asks why the colour differs from on screen simply tell them screen is made of RGB colours and print is CMYK as we described so they will look different because they use light differently. If your project is critical and colours need to be matched this would require a pms(Pantone matching system) as detailed below.
Pantone matching system – PMS
Pantone Inc developed the matching system way back in 1963 to overcome the above problems with RGB and CMYK when a job requires exact colour matching. They are specials or spot colours used and are matched to the pantone booklet either coated, matt or non coated stocks. You can create your artwork and specify this spot colour whilst asking your client to sign off the colour from Pantone colour book. Pantone colours ensure consistency and are accurate with the printer mixing the colours as directed from Pantone. The only downside to this special colour is the cost, much more expensive but worth it if your job requires accuracy in colours.
If your client isn’t colour critical use CMYK and hard copy proof for sign off the peace of mind.