Fruitbasket schema question for both W3C/RelaxNG

[resending from the right email account this time]

A good subject line would be "how to validate complex type instance with
uknown element name".

Consider a fruitbasket element that may contain any number of
[fruit-name] elements:

<fruitbasket>
   <apple taste="red"/>
   <orange taste="red"/>
</fruitbasket>


I short, I want to allow any element inside fruitbasket, as long as it
has an attribute with the name "color". I also want to validate the
attribute value, for erxample it should only allow the colors in my
enumeration.

Can anyone please share his/her lights here? Using

<xs:any namespace="##targetNamespace" processContents="strict"/>

does not work, while

<xs:any namespace="##targetNamespace" processContents="lax"/>

does not signal for invalid elements inside the fruitbasket at all.

Any advice or pointers welcome for both XSD/RNG, as I would like to
offer both in my application.

Manos