Removed different color for caret row in balloon to avoid confusing.

idea/src/org/jetbrains/jet/plugin/codeInsight/EditSignatureBalloon.java

@@ -23,6 +23,7 @@ import com.intellij.openapi.actionSystem.PlatformDataKeys;
 import com.intellij.openapi.application.Result;
 import com.intellij.openapi.command.WriteCommandAction;
 import com.intellij.openapi.editor.*;
+import com.intellij.openapi.editor.colors.EditorColors;
 import com.intellij.openapi.editor.ex.EditorEx;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.ui.popup.*;
@@ -138,6 +139,8 @@ class EditSignatureBalloon {
             ((EditorEx)editor).setEmbeddedIntoDialogWrapper(true);
         }
 
+        editor.getColorsScheme().setColor(EditorColors.CARET_ROW_COLOR, editor.getColorsScheme().getDefaultBackground());
+
         return editor;
     }