To preview colours, touch and hold the colour on the page, then drag across other colours on the page. Release your finger to select a colour.
Change the line thickness: Tap the + or – next to Width.
Change the amount of space between the line or border and the text: Tap the + or – next to Border Offset.
To quickly remove the border or rule, select the text with the border or rule, tap Add a border to an object in Pages on iPad