Without doubt this is one of the most beautiful songs sung by Miku.
Since my translation is more literal, it’s less beautiful than yours.
Please just take it for your information
Flower petals coloured the time of light coral
In the light those petals were fluttering
I should have smiled
* Literally, the phrase would be "In the light flower petals that coloured the time of light coral were fluttering I should have smiled" but it seemed to be too long.
I translated 薄紅 as light coral though, there might be a word that fits better.http://www.colordic.org/colorsample/2279.html
The sandcastle we left behind in those bright days
Will melt into the waves
And surely, the dream will end
*I agree with Lygerzero0zero
When I woke up in a white world
My extended fingers could not grasp anything/ I extended my arms but I could not grasp anything
What did I lose every time the sky I looked up at got closer?
Our shadows reflected in the transparent waves were blue and far
Even just a little
I want to help you
Those intangible things are the only
Things that have not/did not weathered in the time
Even if so many times the sandcastle disappears into the transparent waves
I will make it with you every time it does/disappears and leave it behind
Gathering lights there
*Probably the subject of the second line 何度消えてしまっても is 砂の城sandcastle. 波waves can be the subject gramatically and would be in the usual case. But I think it’s contextually 砂の城 since this phrase seems to make an antithesis of "The sandcastle we left behind in those bright days will melt into the waves" and 透通る波 is not used as a subject in the preceding phrase.
To the distant place where you are/To you who are far distant from me
Those lights will fly across the sky
I want to send you the songs of the sort[kind]/like them
Even though everything I (will) give you
I want to become a star that shines
Somewhere in your heart