The colors in Undertale have significant meanings, more than the obvious. Allow me to explain.

First up, most people reading this probably already know, but still:

Ball Game shows us that these colors represent these soul traits. That said, these meanings show up fairly frequently.

To start with an easy one, Bravery and Patience are orange and light blue. To survive orange attacks, you have to move through them. To survive light blue ones, you have to sit still. Meaning, you have to brave orange attacks and wait patiently through blue ones. Same deal with the orange and blue lasers present throughout Hotland and the CORE.

Green is Kindness. Green is also for healing attacks. Healing is kind, right? Especially for an attack. The green soul mode is also the shield mode, and the green soul’s attack during the Photoshop Flowey boss fight was frying pan throwing food at you. Green has themes of healing, caring and protection.

On to purple, Perseverance. The purple soul mode is only used in one boss fight, Muffet’s. Muffet’s fight is inarguably a difficulty spike, as there are intentional ways to skip it in the game. If you eat a spider pastry during Muffet’s fight, she will immediately spare you because she realizes you are a friend to spiders. Sans hints about this at his hot dog stand:

College here refers to the Temmie Armor, a way OP defense item intended for people who are struggling with the game’s difficulty.

I don’t have much to say about integrity. Maybe some clues lie in the blue text highlights?

One more thing - Sans’s eye lights up light blue… and yellow.

Light blue and yellow. Patience and Justice. 

What does Sans do in the Judgement Hall? He judges you. LV, EXP, sins crawling on your back and all that. Sans waits until the literal last possible moment to intervene in your genocide route, and his special attack, after all the hype, is literally waiting for you to get bored and give up. He’s Patient. 

That’s all I have to say about the topic. Do with this information what you will.