diff --git a/README.md b/README.md
index 262e2f5..8f319c4 100644
--- a/README.md
+++ b/README.md
@@ -117,7 +117,17 @@ Their vertical position can be adjusted with the `position` parameter (between
## Colors on operators
-Colors can be specified with `fill=color` option, e.g.
+The color of operators and wire can be changed with `color=...` options, e.g.
+
+```
+\twocell{((1->1)["\alpha",color=red] * 1) * (1[color=red] * (1->1)["\beta"])}
+```
+
+typesets
+
+
+
+Filling colors can also be specified with `fill=color` option, e.g.
diff --git a/fig/color.svg b/fig/color.svg
new file mode 100644
index 0000000..4f34c82
--- /dev/null
+++ b/fig/color.svg
@@ -0,0 +1,25 @@
+
+
diff --git a/fig/color.tex b/fig/color.tex
new file mode 100644
index 0000000..fef006f
--- /dev/null
+++ b/fig/color.tex
@@ -0,0 +1,9 @@
+\documentclass{standalone}
+\usepackage{satex}
+\usepackage{common}
+
+\begin{document}
+$
+\twocell{((1->1)["\alpha",color=red] * 1) * (1[color=red] * (1->1)["\beta"])}
+$
+\end{document}
diff --git a/fig/fill.svg b/fig/fill.svg
index 7ead766..9a37c56 100644
--- a/fig/fill.svg
+++ b/fig/fill.svg
@@ -1,33 +1,31 @@
-