You may have to use a warmth mat, as coleus seeds require a reliable temperature of 70-75°F to germinate. Location in a sunny windowsill and if ideal, you may deal with the tray with a humidity cover or plastic. two years ago Coleus are my all time favorite plant. https://lionpictures11111.blogocial.com/not-known-facts-about-popular-coleus-cultivars-62767765