Unable to select colour lines

[Anonymous]

Hello. I see some colours lines on the plan views only. I don't see them on elevation or section. I attach a screencast.

1. On the beginning, I thought there may be a cad link, but all these links are not loaded.

2. Another thing I don't understand is why I cannot select those lines in order to delete them.

Help appreciated.

[ToanDN · Accepted solution]

Enable 'Select Underlay Elements'.  I circled it in Red below.