Meters dont read color, merely the amount of light. A red filter generally needs 3 stops extra light to give the same exposure as no filter, so meter without, then with to see if it gives the proper reading. I recommend you do this with all your filters, and check against the filter factor for that color. Yellow needs one extra stop, and is the easiest to allow for. I meter with my L-398 and add one stop for yellow. On my OM-1, I just trust my on-camera meter, I've already run tests and know ahead its correct. For orange or red, I meter, then add the filter, adjust exposure and shoot.