Legend: change of fill color R plot

Question

I was wondering how I could change the fill color of the square next to beta in my legend below to be according to: adjustcolor("blue",alpha.f=0.05) ?

Here is my current R code (with no success):

curve(dt(x,19),-5,5)

legend("topright",legend=c(expression(paste("Power")),expression(paste(beta))),
density=c(15,0),angle=140,fill=T,col=c(adjustcolor("blue",alpha.f=0.05),0))

Answer 1

Something like this should work:

legend("topright",legend=c(expression(paste("Power")),expression(paste(beta))),
       density=c(15,0),angle=140,fill=T,border=c('black', 'blue'))

[EDITED]

legend("topright",legend=c(expression(paste("Power")),expression(paste(beta))),
       density=c(15,NA),angle=140,fill=c("#000000FF", adjustcolor("blue",alpha.f=0.5)),
       border=c("#000000FF", adjustcolor("blue",alpha.f=0.5)))