I always assumed that the suit and Slave 1 were inherited by Boba, but Lucas got the colors wrong because he forgot to watch the original trilogy before filming the prequels.
I used to think perhaps it was Jango’s suit but the colors were starting to fade or something
I think the idea Lucas was shooting for in Attack of the Clones was that they’re the same suits, but repainted a few times and missing some parts by Empire. The Reek on Geonosis puts a dent in Jango’s helmet in about the same spot as Boba’s is dented (despite Jango’s being a dent and Boba’s looking more like blaster damage) and Boba’s armour has a silver base colour, which I feel is a bit of a silly idea.
They “retcon” this, I assume, in The Clone Wars where Jango’s helmet is destroyed in a certain episode (I won’t spoil anything though).
In the EU they have scenes where Boba replaces damaged parts of his armour with other pieces from a collection, which makes sense to me considering the differences between Empire and Jedi.