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The green one, which will be supplemented with some purple variety rhizomes as and when they arrive from the Netherlands, is close to a south-facing window and while there's a Venetian blind the slats are open. Should be getting a decent amount of light, I would've thought. It was sufficiently bright to slightly scorch the leaves on a Maranta leuconeura, so I think it should be enough to keep an Oxalis happy.
Purple one looks like this if you keep it somewhere too dim and let it get leggy