Controlling and manipulating the colour of you photographs plays a huge part in creating wonderful images, whether your aim is to reproduce the colours truly or to change them creatively. There are many things you need to do to ensure that the colours that you end up with on screen represent the ones in the original scene, and there are also many things that you can do to then change them to produce the emotional or artistic effect that you want.
Different Blending Modes can be used on Adjustment layers to control colour in different ways.
Luminosity Blending Mode only affects the luminosity or brightness of an image, so using a Black & White Adjustment layer set to Luminosity Blending Mode can control the brightness of individual colours.
Colour Blending Mode will only effect the colour and not the luminosity or brightness.