** 1. since the remaining testicle grows larger [compensatory hypertrophy] and thus produce more sperms, sperm count will probably remain within normal limits, semen volume is unaffected and normal because 95% is produced by the seminal vesicles, prostate and cowper s glands, so either there is an obstruction or there is a sperm production problem. He would need an evaluation by a urologist experienced in fertility. 2. food that is rich in sulphur [garlic, onions] can make semen yellowish . as the person gets older [aged] his semen may pick up a yellow tint [but age is not a factor in his case] . multivitamins can cause change in semen colour [make sure he is not taking any alternate supplements] . the most common infection causing yellowish/green tinge to semen is epididymitis, which can be easily cured with antibiotic therapy. [may require per rectum examination for prostate infection] 3. This is very natural and a common occurrence among many men, but to alleviate your symptoms kindly consult your Doctor.