Crisp, bright colours are your secret weapon when it comes to replicating natural light in a windowless bathroom. Direct clear of the darker end of the colour range; instead, paint your light versions of warm colours, like buttercup yellow, pink and seaside colour of aqua blue. Select a colour either two or three lighter colours for your trim and ceiling. As well as outlining the area and offering visual contrast, this will draw the eye away from dark corners.
Lighting also plays a big part. Position warm lighting with a dimmer switch over the insignificance and shower to make warm tints sparkle. Want to make an instant update? You can’t go wrong with a large mirror over your insignificance - this will greatly help soften the artificial light.