From your description, it might be a goldenrod crab spider (also called a flower crab spider). These spiders often wait on flowers, including goldenrod, to catch visiting insects.
Goldenrod crab spiders can be yellow or white, and some look greenish. Their colors and markings vary, so the purple coloring on the tops of the legs could fit—but it is not enough to identify the spider for certain. A clear photo, especially of its body and the way it holds its legs, would help.
How it lives
- It usually waits quietly on a flower instead of building a web to catch prey.
- Its front legs point out to the sides, a bit like a crab’s legs.
- It catches small insects that come to the flower.
It is generally not dangerous to people. You can admire it where it is, and avoid handling it. If you share a photo and say where you found it, I may be able to narrow down the identification.