How to edit the style of a connected widget in Bitrix?

Question

css

There is Bitrix CMS, and a callback widget from "Leadback". Make the background of the form opaque.

The widget is connected via a script. The service support said that you can change the transparency in CSS on the site itself. In the console I found a piece of code with the style of this form, when editing in the console itself, everything works out, but I don’t know how to change it permanently. There are no styles in site page templates.

As I understand it, you need to find a file where these styles are written, or create a new one with a changed style, but I don’t know where to add it.
UPD. DECISION.
Let's go: Administration > Content > Site Structure > Files and Folders > CSS > style.css (there is also styleS.css, but we don't need it).
Add to the very end of the file:
#lb_widget-root .lb_widget {
background-color: rgba(255,255,255, 1) !important;
}
And save. Ready!

Answer 1

option 1:
1. create file_name.css
2. write style:

#lb_widget-root .lb_widget  {
  background-color: rgba(255,255,255, 1) !important;
}

3. somehow bind the style file to the desired page (as convenient)
4.???
5. profit!
option 2:
1. find the template file/file.html of the page
2. write the style right inside the file:

<style type="text/css">
  #lb_widget-root .lb_widget  {
    background-color: rgba(255,255,255, 1) !important;
  }
  </style>

3.???
4. profit!
option 3:
1. create a style file / write a style tag inside the template file
2. assign a new class some-class-name-class to the required tag
3. write a style:

.some-class-name-class {
  background-color: rgba(255,255,255, 1) !important;
}

4. ???
5. profit!

Answer 2

When you call setColor you only have two lines of code running

gameColor = clr; // Меняем черный на зеленый
сonsole.log("After: "+gameColor); // After: green

Where is the canvas work? Why should she change?

var game = new GameWindow(500,500, "canv"); // Функции-конструкторы принято именовать с большой буквы
game.setColor("green"); // Присваиваем зеленый цвет

function GameWindow(width, height, id){

  document.write("<canvas width="+width+" height="+height+" id="+id+"></canvas>"); // пиздец, конечно, ну да ладно =)

  this.canvas = document.getElementById(id);
  this.width  = width;
  this.height = height;
  this.color  = "black"; // initial color
  this.ctx    = this.canvas.getContext("2d");

  console.log("Before: " + this.color);

  this.fillCanvas();
}

GameWindow.prototype.fillCanvas = function(){
    this.ctx.fillStyle = this.color;
    this.ctx.fillRect(0,0, this.width, this.height);
}

GameWindow.prototype.setColor = function(color){
    console.log("After: " + color); // After: green
    this.color = color;  // Меняем черный на зеленый
    this.fillCanvas();
}