To force an XSL-FO attribute to inherit the value of another attribute, use the
inherited-property-value:
<fo:block color="blue">
Hello
<fo:block color="yellow" background-color="inherited-property-value(color)">
to you!!!
</fo:block>
</fo:block>
The idea is that the "Hello" foreground will be blue and the "to you" background will be blue (by inheritance), but the "to you" foreground will be yellow.