She added: "I hope everybody will come over and visit it".
"Are we kidding? This is what they worry about when lives could be saved?"
"Think of this as a human story, an opportunity to save lives", Trump said, encouraging the students to change the world in opioid and drug abuse.
The first lady hit the switch to light the tree after her husband did a countdown from 10, urging audience members to join in.
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One man who, in spite the horrific man management of Jose Mourinho , has managed to excel in recent weeks. The performance had lots of good things but also lots of disappointing things.
Addressing the opioid epidemic is a pillar of the first lady's Be Best youth initiative.
- Melania Trump (@FLOTUS) November 26, 2018Despite its festive look, some Twitter users pointed out that the blood red Christmas trees resembled costumes from a popular Hulu series, The Handmaid's Tale. I think they look fantastic (applause).
She didn't lash out at her critics, nor did she back down from her decision.
Trump took questions from a few students who were attending the convocation. And what does the media - I'm telling you, I can't believe this - what are they hung up on with the first lady right now?
Speaking at a panel event at Liberty University in Virginia on Wednesday, Mrs Trump said: "We are in the 21st century and everybody has a different taste. We need to be there for them ... to encourage them and see in themselves their positive character".
Trump included the opioid crisis and how it affects children as one part of her three-pronged platform, "Be Best", which she launched in May.