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We characterize the strength, in terms of Weihrauch degrees, of certainproblems related to Ramsey-like theorems concerning colourings of the rationalsand of the natural numbers. The theorems we are chiefly interested in assertthe existence of almost-homogeneous sets for colourings of pairs of rationalsrespectively natural numbers satisfying properties determined by someadditional algebraic structure on the set of colours.  In the context of reverse mathematics, most of the principles we study areequivalent to $\Sigma^0_2$-induction over $\mathrm{RCA}_0$. The associatedproblems in the Weihrauch lattice are related to $\mathrm{TC}_\mathbb{N}^*$,$(\mathrm{LPO}')^*$ or their product, depending on their preciseformalizations.

On the Weihrauch degree of the additive Ramsey theorem