Why do you think the same color M&M was used in each sample of water?

The candy coating is made up of coloring and sugar. The coloring and the sugar molecules both have positive and negative charges on them. The water molecule has positive and negative charges so it can attract and dissolve the color and sugar pretty well.

Explanation:

go to https://www.acs.org/content/acs/en/education/whatischemistry/adventures-in-chemistry/experiments/dissolving-m-ms.html#:~:text=The%20candy%20coating%20is%20made,color%20and%20sugar%20pretty%20well.

there is none because earth is stationary and flat.