colour/fill/stroke

[ijlyttle]

Hi @wenyuyangpku, @haleyjeppson,

I know we discussed this a little bit during one of our meetings. Here's what I think I remember, so I will rely on you to "fill in the gaps":

In general, ggplot2 colour -> Vega-Lite stroke, and ggplot2 fill -> vega-lite fill.

In Vega-Lite, color can mean stroke or fill, depending on the type of mark.

I remember @haleyjeppson saying something about colour and fill having different meanings in ggplot2, depending on the context.

I'd like to use this issue as a way for us all to come to an agreement on how to navigate this.

[wenyuyangpku]

For now, I just remove color and use stroke and fill to substitute it in Vega-Lite.