What is it important to spread the leaf out on a white tile and not coloured one?

Spreading the leaf out on a white tile is important because the white background contrasts with the colour of the leaf (if it is green), making it easier to observe and document any transparent or translucent areas of the leaf. These transparent or translucent areas can provide valuable information about the leaf's structure, internal features, and even the presence of certain chemicals or compounds. By placing the leaf on a coloured tile, the contrast may be reduced, making it more challenging to accurately identify and document these transparent areas. Additionally, a white background helps to ensure consistent lighting conditions, facilitating accurate documentation and comparison between different leaves or samples.