The stroke color is mixed with the fill color

p5.js Coding Questions
1

I drew black as the stroke color and set 1 as the weight, but the stroke color is not black. Please refer to the picture and code below.

stroke
stroke835×592 203 KB

var canvasWidth = 640;
var canvasHeight = 360;
var blockSize = 30;

function setup() 
{
  var canvas = createCanvas(canvasWidth, canvasHeight);
  background(255,255,255);
  noLoop();
}

function putBlock(x, y) 
{
  strokeWeight(1);
  stroke(0);
	fill(255,0,0);
  rect(x * blockSize, y * blockSize, blockSize, blockSize);
}

function draw() 
{
    putBlock(0,0);
}
2

I’ve tested in Chrome (actualized) It’s black on my pc.