Getting more color on stainless welds

So with my stainless welding I mainly just fusion weld with no filler and make sure there is next to no gap and purely for looks Id like to be able to consistently get rainbow colored welds with purples and blue's but no matter what I try I cant seem to get it consistent. The odd occasion I can get a section to but not sure exactly how. Ive tried going faster, slower. More angle/less, bigger lens/smaller, more/less gas flow. I can either get shiny silver, shiny gold or dull grey. (consistently)

The pics is a muffler delete wank factor exhaust for a customer by request and I settled for shiny gold. I used a #7 cup. 7-10lpm flow and 20amps manually pulsed with foot pedal but would really love to get more color but consistently be able to control it.

The only way ive been able to get it consistent is to weld as above but stop after about 20mm and pull the gas away quickly. but this is no good as its too many starts and stops.

I know purple/blue is steel being oxidised at higher temps so I thought less gas flow, smaller cup, faster travel, more amps would create the condition but I just cant seem to make it happen.

Wow, thanks for the post, thats a lot of work and really nice welds. This is a good question, did you purge this exhaust? I find that purged parts colour better, I have also found that a large cup combined with higher heat and a faster rate of travel will add more blues and purples into the weld area. The cleaner and more polished the material (and the greater the quality of the stainless) the better it should look.