A 65
Yes, the second caster can see the first one. Antimagic field only stops spells and magical effects from functioning inside the area, and it does not block line of effect.
A 66
All of those spells will affect their targets normally.
Cone of cold and flame strike are area spells, and their effects will be suppressed in any portion of their areas that overlap the antimagic field, but since the intended target is not within the field it will not protect him.
Seeking ray and disintegrate are both ray spells. Like the area spells, they are suppressed within the antimagic field; but since the field does not block line of effect, the rays will simply wink out and reappear on the other side as if nothing was wrong.
Orb of force is an instantaneous conjuration spell. This means that the orb is essentially nonmagical after it appears, and it will function normally even against targets inside the antimagic field.
A 67
There is no rules basis for MaxiDuRaritry's claim that painting oneself will block line of effect or protect them from anything. Clothing doesn't break line of effect, why would paint?
I am completely certain I would never allow such a thing to work in one of my games.