sorry for the vague title, but can’t really spot where the error comes from. if you download the VL.ColorThief plugin (nuget install VL.ColorThief -pre), GetColor throws Sequence Contains No Element error. On 2019.1 0975, the help patches work fine.
So, steps to repro :
Open 2019.2
nuget install VL.ColorThief -pre
Open one of the two help patches and navigate to GetColor’s definition, this should pop up :
As a workaround place a SKBitmap.FromImage and SKImage.FromBitmap inside your Bitmap (SKImage) node. For the SKBitmap nodes you need to enable the Obsolete switch in the nodebrowser. The PeekPixels method seems to work when the SKImage is backed by a SKBitmap.