How to fill a rectangle with color?

PdfContentByte canvas = writer.getDirectContent();
BaseColor bColor = new BaseColor(0xFF, 0xD0, 0x00);
canvas.setColorFill(bColor);
canvas.fill();
canvas.rectangle(rect.getLeft(), rect.getBottom() - 1.5f, rect.getWidth(), rect.getHeight());
canvas.stroke();

You are doing things in the wrong order.

You need:

1. Change graphics state (e.g. fill color, stroke color,...)
2. Create path
3. Fill and/or stroke path

You can switch step 1 and 2, but step 3 always needs to be last.

So you should adapt your code like this:

PdfContentByte canvas = writer.getDirectContent();
BaseColor bColor = new BaseColor(0xFF, 0xD0, 0x00);
canvas.setColorFill(bColor);
canvas.rectangle(rect.getLeft(), rect.getBottom() - 1.5f, rect.getWidth(), rect.getHeight());
canvas.fillStroke();

Note that this is also wrong:

PdfContentByte canvas = writer.getDirectContent();
BaseColor bColor = new BaseColor(0xFF, 0xD0, 0x00);
canvas.setColorFill(bColor);
canvas.rectangle(rect.getLeft(), rect.getBottom() - 1.5f, rect.getWidth(), rect.getHeight());
canvas.fill();
canvas.stroke();

In this case, the rectangle will be filled by canvas.fill(), but it won't have any border, because the path created using the rectangle() method has been dealt with when you filled it. No new path has been created between canvas.fill(); and canvas.stroke(); so the stroke() operator won't do anything.