So, after checking out the express reference, I found that req.query.color
would return me the value I'm looking for.
req.params refers to items with a ':' in the URL and req.query refers to items associated with the '?'
Example:
GET /something?color1=red&color2=blue
Then in express, the handler:
app.get('/something', (req, res) => {
req.query.color1 === 'red' // true
req.query.color2 === 'blue' // true
})