You explained it clearly—and you do not need to be an expert to ask for help! I understand that this spider is mostly green, with longer, hairy yellow legs that have purple near the top. It is active and was on goldenrod in South Carolina.
Those clues make a lynx spider one possibility. Some lynx spiders hunt on plants and have long, spiny legs. But I cannot tell which kind—or confirm that it is a lynx spider—from the description alone. Spiders can look quite different depending on their age and the way the light falls on them. The flat-looking face is interesting, but it is hard to use by itself for identification.
Details that could help
- About how big is it, including its legs? You can compare it to a coin or a fingernail without touching it.
- Does it have a round, ball-shaped abdomen, or a long, narrow one?
- Are the hairs soft and fuzzy, or do they look like stiff spikes?
- Does it sit still and wait, or run and jump around?
- Do you see a web, or is it walking freely on the plant?
You do not have to answer every question. Even one or two details may help. Please do not pick it up; just watch it from a safe distance.
Getting a picture, if you want
If you are allowed to use a phone or tablet, ask a grown-up to help take a picture. A clear photo from the side and one from above can be useful. You can also ask a parent, teacher, librarian, or local nature center to help share the picture with a spider-identification group or a South Carolina nature expert.
If you cannot take or upload a photo, that is okay. Your description is a good start, and you were right to point out how this spider is different from the yellow goldenrod spiders you found.