There are several blend modes which are used to mix multiple colours.
1. Normal- In this blend mode top layer is completely dominant and bottom layer is suppressed.
2. Dissolve- In this blend mode edges of top layer get effected and looks as pixelated over bottom layer.
3. Darken/Multiply/Color Burn/Linear Burn/Darker Color- In this they blend and show only dark region of colour and hides light colour.
4. Lighten/Screen/Color Dodge/Linear Dodge/Lighter Color- In this mode lighter colors are shown and darker are hided. This is opposite of above modes.
5. Overlay/Soft light/ Hard light/ Vivid light/ pin light/ Hard mix- In this mode contrastic colors are shown.
6. Difference/ Exclusion/Subtract/Divide- In this mode the inversion of color is shown as example white becomes black.
7. Hue/Saturation/Color/Luminosity- In this mode upper layer colors are mixed and blended to lower layers.
Shortcut to use blend mode is by selecting move tool and using shift + +/- to change in blend modes.