I completely underestimated my own hostas last year, planting small dahlias at what I thought was a safe distance from the crown of a large and very mature specimen. It wasn't until the dahlia stuck a shy little blossom out from under the hosta leaves that I even realized that it was there. If your bulbs are planted under deciduous trees, where they get spring sun, before the trees leaf out to create shade, then you may want to consider using ferns as a way to hide the yellow stuff. There are many lovely ones to choose from, and they add great textural interest to the garden as well. The Autumn fern in the photo here also adds a spot of color - as will the Japanese Painted fern with its fronds of silver and burgundy.
Many people recommend using daylilies.
This works fairly well, but you have to be careful with their placement. You want them in front of the bulbs rather than interspersed. I tried simply planting the two in one bed, not paying attention to what was in front of what, and the only camouflage that I achieved was that the bulb foliage resembled dead daylily leaves. If you start dahlias indoors so that they get a good head start, you can plant them out when the soil warms. Their foliage spreads quickly and can help hide a multitude of evils.