How to make legend symbols transparent using pygmt

I am plotting a map using the pygmt and i set the legend in the left corner of the plot. The legend contain the symbols of black, blue and red and i want to make the black,blue and red legend symbols to 50% transparent

I am using this script for plotting the legend

fig.legend(spec='legend.txt', position='JTL+jTL+o2.8c/6.0+w2.6/1.4',transparency=50,box=True)

The transparency used in the which is 50% does not applicable to the symbols inside the box, its working for the transparency whole content of the box so that box content gets faded.
I hope experts may help me overcoming this problem.

cat legend.txt

S 0.2c it 0.25c black 0.2p 0.5c Events0
G 0.2c
S 0.2c c 0.25c blue 0.2p 0.5c Events1
G 0.2c
S 0.2c c 0.25c red 0.2p 0.5c Events2
G 0.2c

Well, you need to select black@50, blue@50 etc for your legend color. The transparency option in GMT (-t command line) makes everything transparent.