If you have a cold and are not feeling tired or weak from the cold then yes it's safe to drive when you have the cold virus.
But if the cold virus is making your body feel tired or weak and you cannot concentrate properly then you should not drive.
Driving requires lots of concentration so if you need to get somewhere either wait until the cold is over or get someone else to drive you if the cold is too severe.
Driving around town with a cold or flu would be less dangerous though than driving on the highway where you require more focus and attention to the road.
So if you need to drive downtown to the store then that should be okay.
But if you're feeling tired, fatigued, have weakness etc then avoid driving until the flu or cold virus has left your body.
Driving requires lots of concentration and is a big responsibility so if you're not feeling too good then stay home and off the road and if you need to be somewhere have someone else drive you.
Driving when you have the flu is not recommended especially if you feel fatigued and have a loss of concentration.
If the flu isn't too severe yet then driving with the flu is usually safe but when the flu has gotten too severe where your body is weak, you have fatigue and cannot concentrate properly then it would not be a good idea to drive while you have the flu.
I have drove when I had the flu and I was okay but I took less traveled roads where I could drive slower and stayed off main highways and freeways.
But if I felt too fatigued from the flu then I would not drive because you could get into a car accident and if you drive while having the flu and cause a wreck due to the flu then you could be held liable for anything that happens.