Solr - Constrain More Like This Results Only - solr

Question

Let's say I have a particular sweater with code:blue-sweater that is color:blue. I would like to find similar products using the description field, with the constraint that similar products are not blue (-color:blue).
From the Solr wiki:
If you want to filter the similar results given by MoreLikeThis you
have to use the MoreLikeThisHandler. It will consider the similar
document result set as the main one so will apply the specified
filters (fq) on it. If you use the MoreLikeThisComponent and apply
query filters it will be applyed to the result set returned by the
main query (QueryComponent) and not to the one returned by the
MoreLikeThisComponent.
These are the params I'm using; the qt param sets the request handler as MoreLikeThis:
{
q: "code:"blue-sweater"",
qt: "mlt",
mlt: "true",
fl: "description,brand,gender,price",
mlt.boost: "true",
mlt.fl: "description",
fq: "-color:"blue"",
rows: "6",
mlt.mintf: "0",
mlt.mindf: "0"
}
The issue is that I can only specify the FilterQuery param once, which sets fq for both the initial query ("code:"blue-sweater") and for the MoreLikeThis results).
Since the filter of -color:blue excludes my initial query (the blue sweater), I am left with no MoreLikeThis results. How do I get around this?
If the only products in the core are color:blue, I still want to return them, but they should be at the bottom of possible results.
Edit
I did some digging around, and it seems that the only way to boost a MoreLikeThis query is by with mlt.qf:
Query fields and their boosts using the same format as that used by
the DisMax Query Parser. These fields must also be specified in
mlt.fl. (source)
I have tried to do a regular query with the DisMax parser with a value constraint (like in_stock:[* TO 10]), but the constraint on the field value gets ignored entirely. You can only do plain boosts on a field (color^2).
So it seems that this is a limitation of MoreLikeThis relying on the DisMax parser instead of the EdisMax parser.