Slow to Medium · Rule 433
Indication: Proceed, SLOW speed passing signal and through turnouts, approaching next signal at MEDIUM speed.

Mast presentation
High mast signal, triple aspect, inline. top: red; middle: flashing yellow; bottom: green.
A high mast, inline, triple aspect signal displaying red on the top, flashing yellow in the middle, green on the bottom.
From the rulebook page's hidden description — Transport Canada's own wording, left in the page as an HTML comment.