git-gui: Use lighter colors in blame view

The colors I originally picked out on a Mac OS X system look a
tad too dark on a Windows 2000 system; the greys are dark enough
to make it difficult to read some lines of text and the green used
to highlight the current commit was also difficult to read text on.

I also added a third grey to the mix, to try and help some files
that wind up with a number of neighboring chunks getting the same
colors.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

lib/blame.tcl

@@ -42,10 +42,11 @@ field tooltip_timer  {} ; # Current timer event for our tooltip
 field tooltip_commit {} ; # Commit in tooltip
 field tooltip_text   {} ; # Text in current tooltip
 
-variable active_color #98e1a0
+variable active_color #c0edc5
 variable group_colors {
-	#cbcbcb
+	#d6d6d6
 	#e1e1e1
+	#ececec
 }
 
 constructor new {i_commit i_path} {