Colonia is the Spanish word for "cologne" or "perfume". While not an extremely rare word, it's highly specific and central to the song's title and main theme, making it unique to this particular track.
In the lyrics, the singer repeatedly mentions smelling cologne, specifically the scent his ex-partner used to wear. He sings, "Me la paso oliendo esa colonia, así te puedo volver a ver" (I spend my time smelling that cologne, that way I can see you again), highlighting how the scent is a powerful trigger for memories and a desperate attempt to feel close to her. This makes colonia a poignant and memorable word in the context of the song's heartbreak.
This song is about that specific kind of heartbreak where you know something is a bad idea, but you do it anyway. Junior H kicks it off by saying he had to leave because he knew the relationship wasn't right for him. He calls her out directly, saying their connection is just a 'come y vete' [come and go] and that she's only in it for fun. He tells her not to cry because he believes she doesn't feel anything real.
But then the chorus hits, and you realize he's not as tough as he sounds. He says his calls are going to voicemail now, but admits, 'Mentí, las fotos aún están en mi phone' [I lied, the photos are still on my phone]. The most painful line is when he says, 'Como tonto me huelo todo el cologne' [Like a fool I smell all the cologne] that she used to wear. He's trying to move on, but he's stuck smelling her perfume just to feel close to her again. It's a story about trying to be strong after a breakup but getting pulled back in by memories and the lingering scent of someone you can't forget.