Remove Style From Selected (Highlighted) Span / Text In DIV

I have many divs with spans inside(just like it is below-no extra ids,classes for spans:
[...]
<div>
<span style="color:red;">a</span>
<span style="color:blue;">b</span>
<span style="color:white;">c</span>
</div>
<div>
<span style="color:red;">d</span>
<span style="color:blue;">a</span>
<span style="color:white;">a</span>
</div>
[...]

What I would like to achieve: user selects with mouse "ab", click button(input type=button) which remove style from selected span/spans. Similar behavior like it is in TinyMCE.