Thanks Ryo and Pratik.
I faced the issue when I was trying to make the graticule light gray but changing the graticule colors, changes the variable's line plot color also. I hope Pratik's command can work but wouldn't it be nice to have the control on graticule within the plotting command itself?
Yes, such a request is already submitted to the github of pyferret. To summarize the current situation,
1) color=7. . . . works
2) color=blue. . . . works
3) color=(r,g,b) . . . doesn't
4) color=(r,g,b,alpha) . . . doesn't
in the GRATICULE settings. Pratik's method is to utilize (1) and customize the color associated with the number.
On the github,
Ansley shows that you can also specify opacity with method (1). To quote from her message
[To use a normal color]
yes? ppl color 7,100,20,50
yes? PLOT/COLOR=(60,50,20)/GRATICULE="(DASH,COLOR=7)" I[I=1:50]
! Define a gray color with, 50% opacity
yes? ppl color 7,50,50,50,50
yes? PLOT/COLOR=(60,50,20)/GRATICULE="(DASH,COLOR=7)" I[I=1:50]
Cheers,
Ryo