I have hosts with items (net.if.in and net.if.out) tagged with:{}

color = {$MACRO_COLOR}

The value of {$MACRO_COLOR} is assigned to the host owning the item net.if.in or net.if.out.

Then in a host different host, we have a calculated item that looks like this:

{{sum(last_foreach(/*/net.if.in[*]?[tag="color:green" and group="MyGroup1"]))}}

This displays the following error:

Cannot evaluate expression: no input data for function at "sum(last_foreach(/*/net.if.in[*]?[tag="color:green" and group="MyGroup1"]))"

HOWEVER

If I define the tag as:

color = "green"

instead of

color = {$MACRO_COLOR}

the calculated item works.

According to the documentation, I should be able to use user macros for tag values in items: https://www.zabbix.com/documentation/6.0/en/manual/config/tagging

So I guess that there is a bug evaluating the macros in the item tags.