NGS - How to change colour of UnderLine of foldout panel ?

Summary:

We have to change color of this Underline which is present on foldout panel

Tried to apply css.

oj-sp-foldout-panel .oj-sp-foldout-panel-title-underline {
width: 2.25rem;
min-height: .25rem;
max-height: .25rem;
background-color: #f0cc71
}

But this css is not working.

Please suggest the way to change the color of this underline which is present on foldout panel.

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