Make default color in Shape Map transparent

I would like to make the default color in Shape Map 100% transparent. I have this code snippet from deldersveld:

"visualStyles": {
		"shapeMap": {
			"*": {
				"dataPoint": [{
					"defaultColor": { "solid": { "color": "#01B8AA"}},
					"showAllDataPoints": true
				}],
				"defaultColors": [{
					"defaultShow": true,
					"defaultColor": { "solid": { "color": "#DDDDDD"}},
					"borderColor": { "solid": { "color": "#222222"}},
					"borderThickness": 1
				}]
			}
		}
	}
}

Is there a way to change "solid": to something else? Or adding a line that changes the transparency of the defaultColor? Any help would be appreciated.

Alternatively, I could set "defaultShow": false, but then the border is erased as well.

Thanks!