igx-checkbox label color is wrong in 13.0

[kdinev]

Description

The label color of the igx-checkbox is no longer correct in 13.0 as compared to 12.2.

• igniteui-angular version: 13.0.0-alpha.7
• browser: all

Steps to reproduce

1. Define an angular view with igx-checkbox. Note: the form is in a dialog if that makes any difference.
2. Define the following theme

   
   $primary: white !default;
   $secondary: #FF0A3A !default;
   $background: #192053;
   $banner-background: #2C3D93;
   $background-gradient: linear-gradient(to right, $background, #04081D);
   $background-gradient-lighter: linear-gradient(135deg, #2f3978 0%, #10193f 100%);
   $progress-success: #13FF21;

$app-palette: igx-palette($primary, $secondary);

@include igx-dark-theme( $palette: $app-palette );

## Result  
![image](https://user-images.githubusercontent.com/1472513/141303250-66b163b2-9e13-4eba-a4e8-5d0a73521553.png)

## Expected result  
![image](https://user-images.githubusercontent.com/1472513/141303314-64f625be-76ec-4353-8ed2-6d6dcf8820ca.png)

## Attachments  
Attach a sample if available, and screenshots, if applicable.  

[kdinev]

I got this resolved by adding $grays to my app-palette:

$primary: white;
$secondary: #FF0A3A;
$grays: white;

$app-palette: igx-palette($primary: $primary, $secondary: $secondary, $grays: $grays);

@include igx-palette-vars($app-palette);