modify docstring + add to docs

docs/src/reference/export.md

@@ -27,4 +27,5 @@ vtk_grid(filename::AbstractString, grid::Grid{dim,C,T}; compress::Bool) where {d
 vtk_point_data(vtk::WriteVTK.DatasetFile, data::Union{Vector{SymmetricTensor{2,dim,T,M}}},name::AbstractString) where {dim,T,M}
 vtk_point_data(vtk::WriteVTK.DatasetFile, data::Union{ Vector{Tensor{order,dim,T,M}}, Vector{SymmetricTensor{order,dim,T,M}}}, name::AbstractString) where {order,dim,T,M}
 vtk_cellset
+vtk_cell_data_colors
 ```

docs/src/reference/grid.md

@@ -2,4 +2,8 @@
 DocTestSetup = :(using Ferrite)
 ```
 
-# Grid
+# Grid
+## Multithreaded Assembly
+```@docs
+create_coloring
+```

src/Grid/coloring.jl

@@ -142,10 +142,10 @@ end
 @enum ColoringAlgorithm GREEDY WORKSTREAM
 
 """
-    create_coloring(g::Grid; alg::ColoringAlgorithm)
+    create_coloring(g::Grid, cellset::Set{Int}=Set(1:getncells(g)); alg::ColoringAlgorithm)
 
 Create a coloring of the cells in grid `g` such that no neighboring cells
-have the same color.
+have the same color. If only a subset of cells should be colored, the cells to color can be specified by `cellset`.
 
 Returns a vector of vectors with cell indexes, e.g.:
 
@@ -159,9 +159,10 @@ ret = [
 Two different algorithms are available, specified with the `alg` keyword argument:
  - `alg = Ferrite.WORKSTREAM` (default): Three step algorithm from
    [*WorkStream*](https://www.math.colostate.edu/%7Ebangerth/publications/2013-pattern.pdf)
-   , albeit with a greedy coloring in the second step.
- - `alg = Ferrite.GREEDY`: greedy algorithm that works well for structured grid such as
-   e.g. grids from `generate_grid`.
+   , albeit with a greedy coloring in the second step. Generally results in more colors than `Ferrite.GREEDY`,
+   however the cells are more equally distributed among the colors.
+ - `alg = Ferrite.GREEDY`: greedy algorithm that works well for structured quadrilateral grids such as
+   e.g. quadrilateral grids from `generate_grid`.
 
 The resulting colors can be visualized using [`vtk_cell_data_colors`](@ref).