She is referring to ‘'rosy’‘ cause the most popular flowers -for Valentines Day,birthdays,Mothers Day,etc-are roses.They are also a representation to love,life or happines(as in this song).
Ba ba ba ba ba ba
Flowers start to bloom in ever different hue
From violet to pink and blue
I can feel a change, no I am not the same
I'm lucky to be here with you
This feels right feels so bright bright
All the world somehow starts to shine shine
With you by my side
Life is rosy
Ba ba ba ba ba ba
Shades of green melt into tangerine
I watch the sun, it's setting in your eyes
Can you tell I'm wrapped up in your spell
Yeah, it's all good and well
I think I realize
Beautiful yeah it's so wonderful
Oh, darlin' don't you know
That life is rosy
Hey, look at my heart
I think it's the start of something new
Hey, I finally see that life is rosy
Beautiful yeah it's so wonderful
Oh darlin' don't you know
That life is rosy