Trouble With Gray Roots

I did a swatch test using L'oreal Excellence Light Auburn. For various reasons, my hair has not been colored for about 4 months, so there is about 2" of gray at the roots.

The shade almost perfectly matched the older color on my hair. However, there was a definite demarcation line at the gray/colored border. Not hot roots, just the color coming out lighter. It may be something I can live with as there's not that much of a difference, but then again, maybe it does look too obvious.

I left color on the gray for 30 minutes and then drew color down the hair length and left it for 10 minutes. The gray thus received 40 minutes of coloring and the previously colored hair 10 minutes.

Any suggestions? It was an OK color until I can get the gray under control. So close, darn it! I'm pretty much in the dumps and need to get rid of these grays. Makes me feel less frumpy.

Thanks in advance. Really wish I could get to a salon but my health is on and off and I've been basically housebound lately.