diff --git a/src/library/grDevices/man/adjustcolor.Rd b/src/library/grDevices/man/adjustcolor.Rd
index d745018014f..84fa4b02bc9 100644
--- a/src/library/grDevices/man/adjustcolor.Rd
+++ b/src/library/grDevices/man/adjustcolor.Rd
@@ -1,6 +1,6 @@
 % File src/library/grDevices/man/palette.Rd
 % Part of the R package, https://www.R-project.org
-% Copyright 1995-2012 R Core Team
+% Copyright 1995-2023 R Core Team
 % Copyright 2002-2010 The R Foundation
 % Distributed under GPL 2 or later
 
@@ -22,10 +22,10 @@ adjustcolor(col, alpha.f = 1, red.f = 1, green.f = 1, blue.f = 1,
   \item{alpha.f}{factor modifying the opacity alpha; typically in [0,1]}
   \item{red.f, green.f, blue.f}{factors modifying the \dQuote{red-},
     \dQuote{green-} or \dQuote{blue-}ness of the colors, respectively.}
-  \item{offset}{
-  }
-  \item{transform}{
-  }
+  \item{offset}{numeric vector of length 4 to offset \code{x :=
+      c(r,g,b,alpha)}, where \code{x} is the \eqn{[0,1]}-scaled result of
+    \code{\link{col2rgb}(col, alpha=TRUE)}.}
+  \item{transform}{a 4x4 numeric matrix applied to \code{x + offset}.}
 }
 \value{a color vector of the same length as \code{col}, effectively the
   result of \code{\link{rgb}()}.