src/vs/workbench/browser/parts/editor/editorDropTarget.ts/DropOverlay/updateStyles
class DropOverlay:	override updateStyles(): void {
		const overlay = assertIsDefined(this.overlay);

		// Overlay drop background
		overlay.style.backgroundColor = this.getColor(EDITOR_DRAG_AND_DROP_BACKGROUND) || '';

		// Overlay contrast border (if any)
		const activeContrastBorderColor = this.getColor(activeContrastBorder);
		overlay.style.outlineColor = activeContrastBorderColor || '';
		overlay.style.outlineOffset = activeContrastBorderColor ? '-2px' : '';
		overlay.style.outlineStyle = activeContrastBorderColor ? 'dashed' : '';
		overlay.style.outlineWidth = activeContrastBorderColor ? '2px' : '';

		if (this.dropIntoPromptElement) {
			this.dropIntoPromptElement.style.backgroundColor = this.getColor(EDITOR_DROP_INTO_PROMPT_BACKGROUND) ?? '';
			this.dropIntoPromptElement.style.color = this.getColor(EDITOR_DROP_INTO_PROMPT_FOREGROUND) ?? '';

			const borderColor = this.getColor(EDITOR_DROP_INTO_PROMPT_BORDER);
			if (borderColor) {
				this.dropIntoPromptElement.style.borderWidth = '1px';
				this.dropIntoPromptElement.style.borderStyle = 'solid';
				this.dropIntoPromptElement.style.borderColor = borderColor;
			} else {
				this.dropIntoPromptElement.style.borderWidth = '0';
			}
		}
	}