To use Photoshop effectively, one should know the colours and how they co-relate. There are two types of colour models, fundamentally present in Photoshop. On the one hand, there are additive colours, and on the other hand, there are subtractive.
ADDITIVE COLOUR SYSTEM:
Essentially, a colour comprises of three basic colours, i.e., red, green and blue. All the other colours are derived by adding these three colours. Thus, the combination of this colour gives rise to an additive coloured model, which is the RGB model. To choose the RGB mode, choose image followed by mode and finally RGB. On the scale of 0 to 255, these three basic colours can be adjusted. Go “channel” via “window”, and here one can see the contribution of each colour. 4 channels can be found, i.e., RGB which stands for red, green and blue channels.
In the first image, RGB has been selected, and thus it can be seen how the image has been portrayed using red, green and blue. But the picture towards right depicts the contribution of the colour red. The channel will be shown in greyscale by default which can be changed by choosing edit followed by preference and lastly the interface. Click on “show channel” in “colour” to see the channel in colour than in greyscale.
In the third picture, with the presence of green colour the sky has got a bit lighter and the skin darker. The area which has white depicts the maximum contribution of the colour blue. The RGB mode is considered to be the best for graphic designing, image processing and provides more combination of colours in comparison with CMYK.
SUBTRACTIVE COLOUR SYSTEM:
Since we know what additive colours are, the opposite of additive colours is the subtractive colour system. The fusion of light that we can see (reflected) with the light that cannot be seen (absorbed) gives rise to this colour model. Different coloured light is absorbed by different colours of inks. An amalgamation of cyan, magenta and yellow ink absorbs the primary colours such as red, green and blue whose residual is dark brown.
CMYK is the abbreviation of cyan, magenta, yellow and black. Choose image followed by mode and CMYK, to change the mode to the latter.
We can see CMYK in the above pictures which are essentially used for printing. It comparatively gives us less combination of colours than RGB. CMYK makes the images a bit noisier, so it is advisable to choose RGB over CMYK.