Frequency Polygon

Hi, I have been asked to produce frequency polygon for my data. I have two groups of participants(high stress(6participants) & low stress (4 participants) and 10 participants altogether. The frequency polygon I produced seems to look wrong as it does not highlight which group is low/high stress results. It shows generalised result. I tried to divide into two groups but it states data too small to calculate. My graph also shows 6 participants but I have 10 altogether. Can some of guide me please? Thank you.

Thank you Glenn.