To find the percentage of students who voted for green, we can use the following formula:
\[ \text{Percentage} = \left( \frac{\text{Number of votes for green}}{\text{Total number of votes}} \right) \times 100 \]
First, we need to find the total number of students who voted:
\[ \text{Total votes} = \text{Votes for green} + \text{Votes for yellow} = 224 + 576 = 800 \]
Now, we can substitute the number of votes for green and the total number of votes into the percentage formula:
\[ \text{Percentage} = \left( \frac{224}{800} \right) \times 100 \]
Now we calculate \( \frac{224}{800} \):
\[ \frac{224}{800} = 0.28 \]
Next, we multiply by 100 to convert to a percentage:
\[ 0.28 \times 100 = 28 \]
Therefore, the percentage of students who voted for green is:
\[ \boxed{28%} \]