→Why scatter plots instead of colour merge images?: image full size
Far too often, composite/merge images of red and green channels are considered sufficient to demonstrate colocalisation. This is plain wrong. The problems with red/green merge images for colour-blind people aside, there is another very good reason to require scatter plots: the perception of human eyes and brain can be fooled very easily. Just have a look at this image:
Most people might think that the image contains 4 distinct colours prominent spirals are in shades of red and green, with yellow-green and yellow spirals in between, but the yellow and yellow-green actually have <b>exactly the same color!</b> You can verify this yourself by calling File>Open Samples>[[Spirals (Macro)]] in Fiji.