Blue, phew, that's fine.
Coolant level in the "make-up" bottle should usually be checked when cold and be between the marks, it'd be unusual if it was any different for your car.
Check the owners manual for exact directions, check when cold etc.
If it drops too low the first thing is that it draws air back into the system when it cools, which can cause all sorts of niggly issues. The systems are engineered to "de-gass" and push any gasses out of the cap into the bottle (and thus vented to atmosphere) and take liquid back in when it cools down again, keeping it full of liquid coolant.
If it's only a small amount needed and you don't want to buy coolant, then a little de-ionised water to bring it up to at least the min when cold will be fine and will avoid the risk of the system drawing air back in when it cools down, which you really don't want to happen. Ideally add a little Honda coolant.
Systems only lose liquid, they don't create it, so if it's low now it will only get lower.