use chroma red and green for color-green and color-red

[jshawl]

This PR updates the green and red colors to match the green and red provided by chroma. I thought the brighter green was a little hard to read and thought using the existing green on the page would improve the readability.

I also checked that the --success and --error variables were not being used elsewhere:

$ git grep -n -e '--error' -e '--success'
static/main.css:32:    --success: #50fa7b;
static/main.css:33:    --error: #ff5555;
static/main.css:51:    --success: #50fa7b;
static/main.css:52:    --error: #ff5555;
static/main.css:254:  color: var(--success);
static/main.css:258:  color: var(--error);

Before

After

[neurosnap]

Awesome! Thanks so much!