R corrplot: Plot correlation coefficients along with significance stars?

Using R corrplot, I have not found a solution where the correlation coefficients in the boxes are plotted together with their significances, i.e. 0.84*** Here is the code plotting only the significance stars. How can the correlation coefficients be added there?

M<-cor(mtcars)
res1 <- cor.mtest(mtcars, conf.level = .95)
corrplot(cor(mtcars),
     method="square",
     type="lower",
     p.mat = res1$p,
     insig = "label_sig",
     sig.level = c(.001, .01, .05),
     pch.cex = 0.8,
     pch.col = "red",
     tl.col="black",
     tl.cex=1,
     outline=TRUE)

If I add, as by the first answer suggested, addCoef.col = "black", the text overlays the significance stars so they cannot really be seen anymore:

The position of the significance stars is defined by the place_points function within the corrplot function.

Problem:

If both, the correlation coefficients and the significance level should be displayed, they overlap (I took yellow for the stars since I have some issues with colour vision...).

library(corrplot)
#> corrplot 0.90 loaded

M<-cor(mtcars)
res1 <- cor.mtest(mtcars, conf.level = .95)

corrplot(cor(mtcars),
         method="square",
         type="lower",
         p.mat = res1$p,
         insig = "label_sig",
         sig.level = c(.001, .01, .05),
         pch.cex = 0.8,
         pch.col = "yellow",
         tl.col="black",
         tl.cex=1,
         addCoef.col = "black",
         tl.pos="n",
         outline=TRUE)

^{Created on 2021-10-13 by the reprex package (v2.0.1)}

Quick and temporary (you have to re-do this step everytime you newly loaded the corrplot package) solution:

Change the place_points function within the corrplot function. To do so, run:

trace(corrplot, edit=TRUE)

Then replace on line 443

place_points = function(sig.locs, point) {
  text(pos.pNew[, 1][sig.locs], pos.pNew[, 2][sig.locs], 
       labels = point, col = pch.col, cex = pch.cex, 
       lwd = 2)

with:

# adjust text(X,Y ...) according to your needs, here +0.25 is added to the Y-position    
place_points = function(sig.locs, point) {
      text(pos.pNew[, 1][sig.locs], (pos.pNew[, 2][sig.locs])+0.25, 
           labels = point, col = pch.col, cex = pch.cex, 
           lwd = 2)

and then hit the "Save" button.

Result:

library(corrplot)
#> corrplot 0.90 loaded

#change the corrplot function as described above 
trace(corrplot, edit=TRUE)
#> Tracing function "corrplot" in package "corrplot"
#> [1] "corrplot"

M<-cor(mtcars)
res1 <- cor.mtest(mtcars, conf.level = .95)

corrplot(cor(mtcars),
         method="square",
         type="lower",
         p.mat = res1$p,
         insig = "label_sig",
         sig.level = c(.001, .01, .05),
         pch.cex = 0.8,
         pch.col = "yellow",
         tl.col="black",
         tl.cex=1,
         addCoef.col = "black",
         tl.pos="n",
         outline=TRUE)

^{Created on 2021-10-13 by the reprex package (v2.0.1)}