WordPress theme color change option - best way

Hello!

I’m trying to add a color picker option(from Redux) into my theme. When I copy all of the class names from CSS it takes some time. There is any easiest way to get class names quickly?
Let me something clear:

I’m trying to get all class name from my CSS which have color: #fff;

Example:

.class1 {
  color: #fff;
}
.class2 {
    color: #000
}
.class3 {
    color: #fff;
}

I want output like:

.class1, .class3

If there is any good solution for that!

Thanks