This anti-freeze trick does not work easily (probably not at all) for a raw water cooled motor. Unless the motor is hot and thermostat is open (it does not stay open for long anyway as it opens and shuts), the anti-freeze has no way of getting into the cylinder heads and blocks, and simply by-passes them to run straight out of the exhaust pipe. Check out page 11 of this manual....
Your anti-freeze will enter via the hose close to arrow 21, and the coolant entry to the exhaust manifold is that wee T-piece you see under the exhaust manifold (about 3/8 the way along it, from L to R). If the thermostat under the cover at 17 is closed, then the coolant does not enter the T-peice, but just by-passes the motor, runs from R to L along the wee hose at the top (often via raised syphon break), and into the exhaust elbow.
Also check out page 45. Page 10 shows your motor, or very similar, but the principle is the same.
This one needs a bit more thought. Anti-freeze colourant in the exhaust just means that you have anti-freeze in the exhaust... that's all. It does not tell you if it is in the motor.
I have the Volvo MD17C, the three cylinder motor. Yours is very similar to the MD11.
The only way I found to defend that motor against freezing was to drain all three blocks and the exhaust manifold. That's a total of 4 drain plugs (items 19 on my motor picture, items 7 on your motor picture). Also, pull the coolant hoses off the gearbox, and blow the water out of it (by mouth).
If you have a deep bilge, tie some string around the plugs before you unscrew them. The plugs are expensive if you lose them. The plugs have a wee drain screw within them, but I find it just corrodes and jams.
Be careful, at -14C (7F) one night my motor froze on the canal, all the core plugs blew out, but one block was cracked a wee bit. It still weeps, three years later. A weep is not terminal to a raw water-cooled motor, unless it weeps into the oil. (it's not). Such temperatures are rare here, but it was a real heart-stopper, and very nearly wrote off the motor completely. I went back to the boat, started the motor, and water was flying everywhere out of the core plug covers, all of them lifted off, and were at an angle.
I will be happy to steer you through it, if you wish. It isn't a lot of work. The anti-freeze trick is not likely to work at all though, so be careful.