Markers with properties
Plain coordinates only say where something is. A GeoJSON Feature adds a properties object that says what it is — a name, a description, a category, an ID from your database.
{
"type": "Feature",
"geometry": { "type": "Point", "coordinates": [2.2945, 48.8584] },
"properties": {
"name": "Eiffel Tower",
"description": "Sample marker",
"marker-color": "#dc2626"
}
}
The colour is stored with the widely used simplestyle keys (marker-color for points, stroke and fill for lines and shapes), which geojson.io, GitHub's map preview and many other tools understand. When you export to KML, names and descriptions become Placemark names and descriptions, colours become KML styles and all other properties go into ExtendedData — so the markers look right in Google Earth and Google My Maps.