It also happens in 5.2.0-SNAPSHOT.
The problem is the way the highlight effect determines it's end color:
From effects.js, lines 498 and 499:
this.options.endcolor = this.element.getStyle('background-color').parseColor('#ffffff');
The end color is the color of the element to fade or white if that can't be parsed. Since the endcolor is determined while the fade effect is still running, it is some variation of yellow. A solution could be to determine the endcolor on page load and set an explicit end color for the hilight effect to use.