rEFInd identifies the current selection by displaying a partially-transparent icon "between" the OS or tool icon and the background image. The default icon works reasonably well on both solid and image backgrounds, but if you like, you can customize it by creating new icons in PNG or in Microsoft's BMP format or in PNG format. You should create both 144x144 and 64x64 images and tell rEFInd about them by using the selection_big and selection_small tokens, respectively, in refind.conf. (If you also scale your icons, you may want to adjust the selection tile images appropriately. The big image is 9/8 the size of its matching icons, while the small tile is 4/3 the size of its icons.) If you omit the large icon, rEFInd will stretch the small icon to fit the larger space; if you omit the small icon, rEFInd will use the default small icon. Because BMP doesn't support transparency (alpha channels), you must use the PNG format if you want your selection background to show the underlying image beneath it. (You can create the illusion of transparency on a solid background by matching the colors, though.)
+rEFInd identifies the current selection by displaying a partially-transparent icon "between" the OS or tool icon and the background image. The default icon works reasonably well on both solid and image backgrounds, but if you like, you can customize it by creating new icons in PNG or in Microsoft's BMP format. You should create both 144x144 and 64x64 images and tell rEFInd about them by using the selection_big and selection_small tokens, respectively, in refind.conf. (If you scale your icons, you may want to adjust the selection tile images appropriately. The big image is 9/8 the size of its matching icons, while the small tile is 4/3 the size of its icons.) If you omit the large icon, rEFInd will stretch the small icon to fit the larger space; if you omit the small icon, rEFInd will use the default small icon. Because BMP doesn't support transparency (alpha channels), you must use the PNG format if you want your selection background to show the underlying image beneath it. (You can create the illusion of transparency on a solid background by matching the colors, though.)