如何使 mat-option 元素之间的切换（使用上下箭头进行）更具对比度？

Question

Here's my.html-code:

<mat-autocomplete #auto="matAutocomplete" [displayWith]="displayFn">
  <mat-option *ngFor="let option of searchResults" [value]="option">
    {{getHints(option)}}
  </mat-option>
</mat-autocomplete>

And it looks like this, when I switch between elements:

In light theme.

In black theme.

It's hard to see when I switch between elements or focus on one.

So, what I tried: I tried to change styles of element when I get focused on it. As I thought, methods focus() and blur() of element could help me, like here:

<li *ngFor="let item of getParametersWithoutName(); index as i;">
  <br />
  <input [ngModel]="item.name" (ngModelChange)="item.name = $event" (focus)="onParameterFocus(i)" (blur)="onParameterBlur()" />
  <input [ngModel]="item.value" (ngModelChange)="item.value = $event" (focus)="onParameterFocus(i)" (blur)="onParameterBlur()" />
  <br />
</li>

But these methods work only when I use Tab or click my mouse down on element (mat-option), not when I use arrows up and down.

Then I tried to create class, where I'd set styles for an element, and then set this class in html-code. But It didn't help also, No matter what colors I choose for element, it doesn't make it or switching more contrast!