Color blindness is X-linked, which is why it’s much more common in boys. Your family history — especially on mom’s side — is the strongest signal.
Red-green color vision deficiency is X-linked recessive. Prevalence is about 8% in males of European descent and 0.5% in females (Birch 2012). The math is straightforward because the OPN1LW and OPN1MW genes — which encode the long- and middle-wavelength cone opsins — both sit on the X chromosome.
A boy gets one X from mom. If mom is a carrier, that's a 50% chance. A girl needs an affected X from both parents to express it, which is why it's much rarer in girls. A maternal grandfather who's color-blind makes mom an obligate carrier.
Color blindness usually isn't caught until age 4–6 (when kids start matching colors at school) and it doesn't affect their lives the way pop culture suggests. Most color-blind people see colors — just not the same way trichromats do. There's no treatment because there's nothing to fix.
Sources: Birch J. J Opt Soc Am A 29:313–20 (2012), "Worldwide prevalence of red-green color deficiency"; Deeb SS. Clin Genet 67:369–77 (2005), "The molecular basis of variation in human color vision"; AAPOS guidance on pediatric vision screening.