Class your.class
{
Property Colors As list Of %String;


ClassMethod toJson(list) As %String [ SqlProc ]
{
    s json=""
    f i=1:1:$ll(list) {
        s:i>1 json=json_"," s item=$lg(list,i)
        if '$ld(list,i) { s json=json_"null" }
        elseif item="" { s json=json_"""""" }
        elseif $lv(item) { s json=json_..toJson(item) }
        elseif $num(item,".")=item { s json=json_$fn(item,"N") }
        else {
            f c="\","/","""",$c(8),$c(9),$c(10),$c(12),$c(13) s item=$replace(item,c,"\"_$tr(c,$c(8,9,10,12,13),"btnfr"))
            f  q:'$locate(item,"[:cntrl:]",0,j,v)  s $e(item,j-1)="\u"_$e($zh($a(v)+65536),2,5)
            s json=json_""""_item_""""
        }
    }
    
    q "["_json_"]"
}
}

select your.class_toJson(Colors) from your.class

gives you the expected result . If you prefer  a direct  use of globals, then use

write ##class(your.class).toJson($lg(^your.global(theOID),theSlotNumber))

my quick test says there are two chars, CR and LF, on an AIX and on Ubuntu

USER>s str=##class(%GlobalCharacterStream).%New()
USER>d str.WriteLine("Test")
USER>d str.Rewind()
USER>zzdump str.Read(100)
0000: 54 65 73 74 0D 0A                                       Test..
USER>
​USER>w $zv
Cache for UNIX (IBM AIX for System Power System-64) 2017.1 (Build 792U) Mon Mar 20 2017 19:19:37 EDT
USER>

-----------------

USER>s str=##class(%GlobalCharacterStream).%New()
USER>d str.WriteLine("Test")
USER>d str.Rewind()
USER>zzdump str.Read(100)
0000: 54 65 73 74 0D 0A                                       Test..
USER>
​USER>w $zv
Cache for UNIX (Ubuntu Server LTS for x86-64) 2017.1 (Build 792U) Mon Mar 20 2017 19:22:31 EDT
USER>

Maybe, your problem has nothing to do with Cache?

Regards,

Julius