you can add more ungu to make it clear like -> kemeja ungu dan dasi ungu saya.. although kemeja dan dasi ungu saya should be accepted

Hai! In Indonesian, when you want to translate the "copula" + mine (or another pronoun), I think the Indonesian "milik" (or "punya", meaning "to belong") could be used.

For example:

Using the two items, 1 shirt, 1 purple tie (as in your example)

There are some possible translations here.

One shirt and one purple tie are mine. / Satu kemeja dan satu dasi ungu milik saya.

A shirt and a purple tie are mine. / Sebuah kemeja dan sebuah dasi ungu milik saya.

The (This) shirt and the (this) purple tie are mine. / Kemeja ini dan dasi ungu ini milik saya.

The (That) shirt and the (that) purple tie are mine. / Kemeja itu dan dasi ungu itu milik saya.

Also, "milik saya" can be replaced as "milikku". Perhaps, there are more examples to translate these sentences using "milik" and "punya".

It is known that in some Indonesian sentences, the copula can be dropped. And, I think this is one sentence ("Kemeja dan dasi ungu saya.") that is not using a drop in the copula, because there is no copula here. I think this construction is functioning as a noun phrase with the possessive (saya), and it cannot have a copular verb.

I would like to know if this can function differently when the language is colloquial.

Then, I think I would not report this translation.

Selamat belajar!