S. R. Faruqi:

To speak of a ruin as .sad rang is very fine. The colloquial expression kuchh to bhii has also been used very well. The second line too, because of the idioms ko))ii ghar-saa ghar and kyaa naql karye ('how would you express'), has become very trim. With regard to a 'house', too, .sad rang is very fine, because in a house oils and colors are used. In this regard, it's also been shown that much ruin has come to the house, but nevertheless at least some shine and vitality has remained. It's a verse of great 'mood'.

FWP:

SETS == IDIOMS
MOTIFS == HOME
NAMES
TERMS == MOOD

Oh, this is an adorable verse! It's one of Mir's brilliant ones, in which the juxtaposition of seemingly simple, colloquial little phrases adds up to a sudden rush of-- of what? Emotion? Insight? Enjoyment? Appreciation? Melancholy? All of the above, no doubt, plus a never-satisfied, never-satisfiable demand that one decide what it means to call the heart 'a home that was a home', so that one can catch a glimpse of what that 'something' that has remained might be. (Mir uses the same idiom in {1577,5} too.)

SRF points to the colloquial kyaa naql karye , and equates naql karnaa with 'to express' [bayaan karnaa]. But in addition, there are so many other meanings for naql , and almost all of them are relevant and even piquant (see the definition above). Just to run through the list is a pleasure. Then, the juxtaposition of the nostalgic claim that the heart is 'a house that was a house' strongly suggests that since the (partial) ruin of the heart, the speaker has not had any other real home (no home that is a home); nor, since the heart was inimitable in some inexpressible way, will he have any real home in the future.

Compare Ghalib's own brilliant use of one of the same idioms, also in the context of remembering a home:

G{35,8}