Coloruid is a flood-fill puzzle. The board is divided into coloured regions, and each move recolours the region you're standing in — merging it with any adjacent regions of that colour. The goal is to make the whole board one colour within a set number of moves.
It's a genuine logic puzzle with a clean minimalist look: the optimal solution is usually not the move that captures the most area immediately, but the one that sets up a bigger merge next turn.
A flood-fill puzzle — each move recolours your region and absorbs adjacent regions of the same colour. The aim is a single-colour board within a limited number of moves.
Pick the colour that connects the most separate regions rather than the one covering the most area. Setting up a large merge for next turn usually beats a big merge now.
Yes — tap a colour. Nothing to install.