My favorite song was end of the Rainbow. It made me tear up. ;-; It reminded me of the good times in my childhood. It really hits hard me as a 27 year old guy.
I'm not going to deny that in my opinion, most of the songs in this special probably weren't the 'strongest' that MLP has ever put together. If anything, I initially thought this special felt more like another 'Equestria Girls' type of special given how most of the songs just have this E.G. feel to it. But if I had to name a song that is 'tolerable' at best, I have to go with 'Living in Color' because I will admit the tune is catchy enough that it warrants a pass. It does touch on the issue not just on living a world of vibrant colors and unique individuals, but to have hope that so long as the community stands together we can truly stand as one cohesive unit and thereby proving what makes their world 'Great Again' (And not for reasons trying to be forced into our craniums). As for the other songs...
Rainbow Roadtrip felt the 'closest' to an opening of E.G. girls song and End of the Rainbow... I don't know the lyric choices, while trying to help set the backstory on the town's predicament, just came off as rather odd for me. And on the latter note, for me it just wasn't as strong a song as the cast tried to make it out to be (Though I respect that they tried their best with what they got).