RefColorSync is a free Aseprite extension that automatically updates your foreground color based on the pixel under your cursor on a reference layer — no more constantly switching to the eyedropper tool.
How it works:
Move your cursor over your reference image while it sits on a named layer (e.g. “Reference”), and app.fgColor updates in real time. Hover → color updates → start painting immediately.
Features:
Real-time color sampling as you move the cursor
Configurable reference layer name (works with layers nested in groups)
Composite mode — sample from the final flattened image instead of a single layer
Option to ignore transparent pixels so they don’t reset your color
Adjustable polling rate (15–40 Hz) to balance responsiveness and CPU usage
Full support for RGB, Indexed, and Grayscale color modes
Settings persist between Aseprite sessions
Limitations:
Aseprite’s Lua API doesn’t expose a hook for “during an active brush stroke,” so the color updates based on cursor position rather than mid-stroke. In practice it feels natural: hover → color updates → paint.
Requirements: Aseprite v1.3+ (uses the app.editor API). Works on Windows, macOS, and Linux.
Download & source: