Starting from version of SEO Layered Navigation Plus extension, you can easily set category-specific filter labels. Here is how:

  1. Open category in which you'd like to change filter label.
  2. Go to "Custom Design" tab.
  3. In "Custom Layout Update" field, add: 
    <reference name="mana.catalog.above_products.nav">
        <action method="setCategoryLabel"><value>More Electronics</value></action>
  4. Instead of above_products.nav, you may use leftnav or rightnav (to specify in which layered navigation you intend to do the change).
  5. Instead of Category, you may write Color, Price, etc (take attribute code, like some_attribute_name and remove underscores and capitalize first letters, like SomeAttributeName).
  6. Save category.

Please note that by default Magento applies layout updates to subcategories. If you'd like NOT to propagate the changes into subcategories, please open each subcategory and set Custom Design -> Use Parent Category Settings to "No". Please also note that in such cases, if you apply a category filter in parent category, then "Custom Layout Update" field will still be used from parent category.