title: Change label color when input is focus
body: <p>I need that when the focus is in the input, the label changes color, however, in my structure does not work. I'm using Bootstrap 4, Angular 5+ and my form is horizontal and vertical.</p>
  
  <p>here is the html:</p>
  
  <pre><code>            &lt;form&gt;
              &lt;div class="col-lg-12"&gt;
                  &lt;div class="form-row"&gt;
                      &lt;div class="col-12 col-xl-4 col-sm-12 col-md-4"&gt;
                          &lt;label for="rg"&gt;Número do RG&lt;/label&gt;
                          &lt;div class="input-group"&gt;
                              &lt;input [(ngModel)]="dados.rg" name="rg" id="rg" type="text" class="form-control"&gt;&lt;span class="separator d-none d-md-block"&gt;-&lt;/span&gt;
                          &lt;/div&gt;
                      &lt;/div&gt;
  
                      &lt;div class="col-12 col-xl-4 col-sm-12 col-md-4"&gt;
                          &lt;label for="data"&gt;Data de emissão&lt;/label&gt;
                          &lt;div class="input-group"&gt;
                              &lt;input [textMask]="mask" id="data" [(ngModel)]="dados.data" name="data" type="text" class="form-control"&gt;&lt;span class="separator d-none d-md-block"&gt;-&lt;/span&gt;
                          &lt;/div&gt;
                      &lt;/div&gt;
  
                      &lt;div class="col-12 col-xl-4 col-sm-12 col-md-4"&gt;
                          &lt;label for="orgao"&gt;Orgão Expedidor&lt;/label&gt;
                          &lt;ng-select class="custom" [(ngModel)]="dados.orgaoExpedidor" id="orgao" name="orgao" (change)="onChange($event)"&gt;
                              &lt;ng-option *ngFor="let orgao of orgaos" [value]="orgao.value"&gt;{{orgao.label}}&lt;/ng-option&gt;
                          &lt;/ng-select&gt;
                      &lt;/div&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
              &lt;div class="col-lg-12 input-radio"&gt;
                  &lt;div class="form-row form-inline justify-content-center"&gt;
                      &lt;label class="radio-label"&gt;Sexo&lt;/label&gt;
                      &lt;div class="btn-group" btnRadioGroup [(ngModel)]="dados.sexo" name="radio"&gt;
                          &lt;label class="btn btn-info" [value]="Masculino" btnRadio="Masculino" tabindex="0" name="masculino" role="button"&gt;Masculino&lt;/label&gt;
                          &lt;span class="separator"&gt;-&lt;/span&gt;
                          &lt;label class="btn btn-info" [value]="Feminino" btnRadio="Feminino" tabindex="0" name="feminino" role="button"&gt;Feminino&lt;/label&gt;
                      &lt;/div&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
          &lt;/form&gt; 
  </code></pre>
  
  <p>in scss I do it like this:</p>
  
  <pre><code>    input:focus {
      border-color: $verde;
      color: $verde;
  } 
  </code></pre>
  
  <p>I tried like this:</p>
  
  <pre><code>    input:focus + label {
      border-color: $verde;
      color: $verde;
  } 
  </code></pre>
  
  <p>but it did not work, and the input lost its color</p>