Turn off String Grid red border of selected cell?

[PJW]

I know it's a two years after your post, but did you look at

FocusColor:     The color used to draw the current focused cell if UseXORFeatures is not set; by default this is clRed.

FocusRectVisible   :  Turns on/off the drawing of focused cell.

I beleive those two properties will do what you are/were looking for.