About changing the color on a staff

If you right click the staff and choose staff/part properties you will see a black rectangle next to Staff line color: You can click this and change the lines to any color you like.

Individual elements have a similar option in the inspector (F8). Right click an item and use Select>All similar items in the same staff and you can change the color every barline for example at once.

The HTML# at the bottom to the right of center in the color selector dialog is the color number. So if you want the barlines the same color as the staff lines, copy the number from the staff lines dialog and paste it into the barlines dialog.