I can't remember the significance of blue vs reds roses?

Same,,

Kihoon never got to tell yeon the meaning of the blue flowers bc when he had gone back to tell him, the flowers were on the ground and yeon was gone. So I’m assuming it meanst he thought that yeon disliked blue flowers hence why he got him a red one?? I could be wrong tho!

I think its because during the historical time which is their first timeline there is a blue colored flower gem that they cherish since it symbolises their feeling with each other and from what I remember Kihoon carried that when he was sent to a war to remember Yeon. And since kihoon remember their past life he also got yeon the same colored blue flowers to yeon before the flashback happen. So I think since now that Kihoon doesn't remember a thing he got Yeon the most common colored of rose which is red. (Sorry for the confusing explanation)