To determine which proportion correctly describes the relative amounts of each color, we need to compare the number of red blocks to the number of green blocks in each group.
Let's start with option A: 15/45. This proportion represents the number of red blocks to the total number of blocks in the first group. However, we also need to consider the number of green blocks in the first group.
Next, let's look at option B: 1/3. This proportion also represents the number of red blocks to the total number of blocks in the first group. However, it does not consider the number of green blocks in the first group.
Now, let's consider option C: 15/45 = 90/30. This proportion compares the total number of red blocks and green blocks in the first group to the total number of red blocks and green blocks in the second group. However, we are looking for a proportion that describes the relative amounts of each color within each group, not between the two groups.
Finally, let's look at option D: 15/45 = 30/90. This proportion correctly describes the relative amounts of each color within each group. It compares the number of red blocks to the number of green blocks in the first group, and then does the same for the second group.
Therefore, the correct proportion that describes the relative amounts of each color within each group is option D: 15/45 = 30/90.