More work on porting diff kitten

tools/tui/loop/api.go

@@ -381,3 +381,17 @@ func (self *Loop) Quit(exit_code int) {
 	self.exit_code = exit_code
 	self.keep_going = false
 }
+
+type DefaultColor int
+
+const (
+	BACKGROUND   DefaultColor = 11
+	FOREGROUND                = 10
+	CURSOR                    = 12
+	SELECTION_BG              = 17
+	SELECTION_FG              = 18
+)
+
+func (self *Loop) SetDefaultColor(which DefaultColor, val style.RGBA) {
+	self.QueueWriteString(fmt.Sprintf("\033]%d;%s\033\\", int(which), val.AsRGBSharp()))
+}