Blue line on pcb editor

Hi, Learning to make a pcb with kicad so please be patient. I am copying from a tutorial with battery, resistor and led. No more white lines on pcb editor. I have drawn lines (red) from led to battery and led to resistor. Was white lines here but now red.
However there is a blue line very straight from battery to resistor. If I draw a red line it is a zig zag line and the blue line remains on the editor. Can I just keep the blue line because it is a straight line from the battery to the resistor? It looks like I can’t remove the blue line. Please advise. Thanks.

What version of KiCad do you have?
In fairly recent versions the backside copper (B.Cu) layer is blue, so you might have drawn a copper trace there ‘by accident’.

I don’t use default colors so I’m not sure what you describe.
May be (only may be) the blue line is the connection line (telling you what you should connect with what) and your red line is not a track but a graphic line so it not makes connection and blue line not disappears.
If you have added a screen shot it would be easier to understand the problem.

The white lines are “ratnest” lines. These show which footprints need to be connected together.
The red lines are top copper layer of the PCB
The blue lines are bottom copper layer of the PCB

If you ever have any doubt about which colour is what, check the "Appearance Manager on the RH side of your screen. Clicking the “eye” beside the colour sample will turn that layer on or off, for your own confirmation.

Thanks for that.I only want one layer. I don’t know how that came about. So where do you select just a single layer at the outset?
My red lines did a short horizontal run then a straight diagonal run. How do you make it straight all the way? The ratnest lines were straight all the way and no cross overs after I did a bit of moving and rotating.

You’re stuck with 2 layers. To overcome this problem you just use one layer.
Your screen shows your view looking down on the board, as if that board is resting on your desk.
If you are using surface mount you may wish to use the Top Layer. If through hole, you will want the bottom layer. If both THT &SMD you will want the bottom layer. Mount the THT on the top then Flip the board to locate the SMD.

PCB editor / File / Board Setup has a lot of requirements.
To work with a layer click on the appropriate layer color in the Appearance panel on the RHS. A blue triangle will show.

There is much information in “Getting started with Kicad” in “Help” at the top of any Kicad page.

version 7. Yes another reply told me that is what happened. Need to know how to set 1 layer from the outset. Don’t have any idea how 2 layers came about.
The red lines did a zig zag. The white lines were straight. How do I get a straight line when I draw one? Tried to go straight but zig zags all over the place.
Instructions say to click on one side of the white line and then click at the other end. When I try this I am dragging the red line with my cursor from one end to the other with a little + icon. This seems to be where the zig, zag comes from. Instructions say to press x to draw the line and thats when the icon pops up. Should I just do this; Press x and then click at one end of the white line and then somehow cancel the x. Then repeat this at the other end of the white line. This may give me the straight line as with the white line. Perhaps I should be holding down x and then left click then releasing the x key. But the instructions don’t say this.

I only work with THT so the printed circuit is on one side and the components on the other. SMD components are on the same side as the printed circuit. So then I need to select blue?

Correct.

So delete all the red then select the bottom layer (blue).

You can’t delete the red tracks if you are on the blue layer, so select red, delete tracks, select blue and draw.

It is possible but tell us what for?
Standard for designing PCB is to not route tracks straight from one pad to the second. Using limited number of directions (90° and 45°) help to organize tracks at PCB.
It looks that you don’t know what is the result you are going to get so here is en example of my PCB: