What does the gold beam above a Foundable mean?
According to this video (starting at 42 seconds), it indicates the difficulty of the Foundable
Yellow = Medium
Orange = Severe
Red = Emergency
Also, if you view this link it says the following:
Keep your eyes peeled for a beam of light shooting up from the Traces you see in the world, these are high-risk Foundables, and as such are worthy of your time.