My cum is really white is that normal?

Yes: Normal color os white or slightly off white/yellowish, oralmost clear depending upon your volume of seminal fluid.

Probably not a probl: This may be due to a variety of factors but most are benign and would not effect you or your partner so long as you have no pain with ejaculation. Consider getting a semen analysis which would rule out infection or other less less issues.

Normal: Absolutely normal. White to off white to yellow tinge is normal. No brown or red or other colors. You should see a urologist if these other colors appear.