If you want to layer a texture containing an alpha channel onto another texture/colour, you can do so using a Lerp, where the A output from the Sample Texture 2D is connected to the T input. The A input would be the colour of the Base/Background while B input would be the colour of what you want to Layer on top. If you don’t have a texture with an alpha channel, you could also use a procedural shape (or a channel from another texture) as the T input. This should be a float value, commonly referred to as a mask. In this case the noise texture is used to interpolate between two colours (blue, green). Then the result is masked using an Ellipse to layer it on the background (same “Base Color” group as used in previous example)