5 days after 3rd FUE Hair Transplant what's the best solution for my earlier FUT scars? (photos)

If you keep your hair at 1 inch in the donor area, I would suggest micropigmentation. That would take away the color contrast that you see between your darker hair and the lighter scar tissue. You could put grafts into the scar but the visual difference with micropigmentation may be equal to or better than grafting and less invasive with an easier recovery. If you aren't satisfied with the micro, you can always choose to do grafts later on, but you may not have to. Find a place that has lots of experience in donor scars. 

Scalp MicroPigmentation can be very effective is disguising FUE or strip scars.  It is best to see  a doctor for a consultation.

FUE will camouflage the FUT scar
with permanent hair. We do a fair number of these scar revision surgeries, see
our website.  Once the grafts/hair grows
it is difficult to find the old FUT scar on the scalp.  SMP on the other hand will hide the scar with
a non-permanent tattoo-like pigment however, every 2 years you will need to
repeat the procedure.

micropigmentation dye will fade away in time and scar will be revisible. But if you have a 300-400 grafts FUE transplantation in the scar , it would conceal the scar forever and that procedure soften the scar and ypu would have a better texture of hard scat tissue because of stem cell activity of dermal papillar cells  those transplanted in to the scar with hair bulb.

You can have either SMP or have FUE grafts placed in your scar, both options if done correctly should conceal your scar nicely. 

The best approach to strip scars is scalp micropigmentation, something we do all of the time. See below in the web reference which shows scars treated of all types