"Lavender's Blue" is a traditional Nursery Rhyme for children. The song has been adapted several times by popular artists in the 20th century, often as a love song which has kept the idea in the collective consciousness. The original song is about flowers and kings and queens. The PDF sheet music, Midi and Mp3 files for this melody can be downloaded using the links in the left-hand menu.
The image below is the first page of the sheet music, and here you can download the full sheet music for Lavender's Blue for piano in PDF format.