Put water, sugar, and salt (if using) in a medium saucepan, stir, and bring to a boil.
Lower to a simmer and let mixture simmer for about 10 minutes, until sugar has completely dissolved and syrup has thickened a bit (it will continue thickening as it cools).
Remove saucepan from heat and stir in dried lavender. Cover saucepan and let steep for about 10 minutes to infuse lavender flavor.
Push syrup through a mesh sieve to strain out lavender buds and into an airtight container like a mason jar or bowl. Stir in food coloring if desired.
Let syrup cool completely before using. Store in an airtight container in the fridge for up to a month.