trihybrid cross of TtGgRr x TtGrRr with punnett square, genotypic ratio, and phenotypic ratio? -PLEASE HELP!!!?

Punnett squares can get really scary looking once you get past dihybrid crosses--but you can do it! See the link below for a really good step-by-step explanation. The individuals you list are heterozygotic at all 3 alleles. Remember that Mendelian genetics assumes independent assortment so:

Each parent will pass on one of these 8 possible genotypes: TGR, TGr, TgR, tGR, Tgr, tGr, tgR, tgr
so your punnett square is 8x8, for a total of 64 squares. However, this doesn't mean that there are 64 different genotypes! Some genotypes get repeated. Here is the full list:

ttggrr: Ttggrr: TTggrr: ttGgrr: TtGgrr: TTGgrr :ttGGrr :TtGGrr: TTGGrr: ttggRr: TtggRr: TTggRr: ttGgRr: TtGgRr: TTGgRr: ttGGRr: TtGGRr: TTGGRr: ttggRR: TtggRR: TTggRR: ttGgRR: TtGgRR: TTGgRR: ttGGRR: TtGGRR: TTGGRR
in a ratio of 1: 2: 1: 2: 4: 2: 1: 2: 1: 2: 4: 2: 4: 8: 4: 2: 4: 2: 1: 2: 1: 2: 4: 2: 1: 2: 1

phew.

The phenotypes are much easier, because many genotypes produce the same phenotype (e.g. ttggRr = ttggRR)

The phenotypes this cross produces will be
tgr:Tgr:tGr:TGr:tgR:TgR:tGR:TGR in a ratio of 1:3:3:9:3:9:9:27