Before Version 6, the default option was to use the colour shown in the brush drop list. The colour only changed when the user applied a line colour manually. Since version 6 (Designer Pro 6 and Photo graphic Designer 6), new brush lines always pick up the current line colour following the idea that when a new object is created, the current colours are applied to it. If GNOMRA is disabled then the new brush line will apply the default line color.
If you want to have a line without a line colour, i.e., picking up the original brush definition, you need to disable the option to override the colour for this particular object, so click on "Edit brush...", "Fill properties", "Local colours replace": "No brush colours".
At present, brushes are not fully GNOMRA compliant. GNOMRA only picks up the brush type and the applied line colour but not the applied "Local colours replace" option. For newly drawn lines, the "Local colours replace" option always defaults to "Named brush colours". Previously, it defaulted to "No brush colours".