A quick look at Wikipedia gives you the following as Steve' list of basses over the years:
Fender Precision Bass Copy: White, white pickguard, maple neck.
Fender '70s Jazz Bass: Sunburst w. tortoise pickguard, rosewood fretboard.
Fender '70s Precision Bass: Pearl White w/ West Ham crest and blue/red pinstriping (formerly
white, then black, then blue sparkle), mirror pickguard (formerly black), maple neck.
Fender '70s Precision Bass: Blue / silver crackle finish (formerly white, then red sparkle), mirror pickguard (formerly black), maple neck.
Fender 1959 Precision Bass: Chess finish (formerly fiesta red or 'salmon pink' as described by Steve in a 1992-era Bass Player magazine), mirror pickguard (formerly gold anodized), maple fretboard (formerly rosewood).
Ibanez Roadster Bass: Black, maple neck (White pickups).
Ibanez Roadster Bass: Black, maple neck (Black pickups).
Danelectro Longhorn Bass: White, rosewood fretboard.
Fender '80s Precision Bass: Red, mirror pickguard (formerly black), maple neck.
Fender '80s Precision Bass: Red, black pickguard, maple neck.
Fender '80s Precision Bass: Red, black pickguard, rosewood fretboard.
Lado Steve Harris Signature Unicorn Bass: Blue w. Unicorn graphic, rosewood fretboard.
Lado Super Falcon Bass: Blue w. Falcon graphic, rosewood fretboard. (He's been using two such basses, one being a proto-type and was delivered back to Lado.)
Unknown brand: Natural, rosewood fretboard.
Unknown brand, possibly a "small luthier" bass: Golden, rosewood fretboard.
Fender '80s Precision Bass: Black, white pickguard, maple neck.
Ovation Acoustic Bass: Black, rosewood fretboard.
Fender Steve Harris Signature Precision Bass: Blue, wine-red pickguard, maple neck.
Guild Acoustic Bass: Black, rosewood fretboard.
Fender Special Precision Bass: Sunburst, white pickguard, rosewood fretboard.
Fender Special Precision Bass: Black, golden pickguard, maple neck.
Here's the Lado for some of the Powerslave promo shots and videos.
This is the oldest shot I can find - probably circa '77/'78.
