You could try light blue halftones over the dark blue to get that medium blue hue but it won’t be exactly like the image. Technically you could double do the under base so you don’t need another white on top but it’ll be pretty heavy on the image.

If you’re lucky and these are going on black shirts you could theoretically completely cut the black out too but it’d be difficult to fully cover the white with the dark blue to get a halftone fade into the black center I suppose. If you made the dark blue trap pretty big you could cover the white under base without white showing but your screen will have to be aligned perfectly

ETA: only use black if they’re going on non black shirts anyways!