1st. looks like a good weld...but actually it isn't correct. Notice how grey the weld looks...that's running too hot...may get a decent weld, but wont pass a weld test. The heat lines should also be close to the weld like in pic 2. Quick evidence of too much heat, that you can see while welding, where you cannot see the grey color while welding.
2nd. this is exactly what a good stainless weld looks like. some pinks and blues...NO GREY. this is correct heat.
Stainless needs to be back purged with argon. If you don't, then the chromium comes to the surface as chromium oxide and will lead to cracks (sometimes immediately visible) and ultimately a short weld life. So if you do tubing, the tube needs to be taped shut and filled with a constant flow of argon through it. If you do this, then the inside of that weld will look exactly like the outside...if not then you get the Cr-oxide like this..
The funny thing about SS is that when you are having trouble...turn the heat (amps) DOWN....where as with regular steel you may want to go UP.
If you have access to a TIG machine with PULSE...USE IT. It controls the amps in a square wave and sort of clips it...prevents excess heat going into the metal and causing the chromium to surface. If you don't have pulse...then you strike an arc...make a pool, dab, then reduce the arc to almost nothing allowing the puddle to almost cool off...then move, and repeat. You cannot (easily) weld SS in a normal flowing line like with 1018....unless you are DEAD on with you heat and speed of travel, or use pulse...then you can weld it like butter.
You can polish off the colors after you are done and get a pristine weld like below.
