In HM8.0,

In File: TComDataCU.cpp
In Funct: TComDataCU::xGetColMVP()

Colocated picture is selected as follows:
use coldir.

TComPic *pColPic = getSlice()->getRefPic( RefPicList(getSlice()->isInterB() ? getSlice()->getColDir() : 0), getSlice()->getColRefIdx());

As per JCTVC-J1003_d7.doc section 8.5.2.1.7
"– If slice_type is equal to B and collocated_from_l0_flag is equal to 0, the variable colPic specifies the picture that contains the collocated partition as specified by RefPicList1[ collocated_ref_idx ]."

Not sure but it seems the above mentioned code should be as follows:

TComPic *pColPic = getSlice()->getRefPic( RefPicList(getSlice()->isInterB() ? (1-getSlice()->getColDir()) : 0), getSlice()->getColRefIdx());