Ash vs violet self tan undertones on very fair skin?

I think I’m finally starting to understand why self tan looks so different on me depending on the product and body area.

I have very fair neutral/cool leaning skin and tend to pull warm/orange easily. I recently tried a violet-based express tan and noticed my arms looked slightly warmer, while my legs sometimes looked more neutral/brown (although still slightly warm in certain lighting).

Now I’m wondering if:

• some people just need more depth for tans to read more neutral OR
• if ash-based tans actually develop noticeably cooler than violet-based ones on very fair skin.

Not really looking for general recommendations — mostly curious about ash vs violet undertones specifically.