Does my dad's tux need to match the color of groom and best man?

Nope-- actually, its a bit more appropriate for him to wear a different color. No need to spend additional money

Our fathers are wearing black suits and FH is wearing a tan suit.

I think a black tux would look WAY more formal than what your FH and Best Man are wearing. It looks like a suit, not a tux, and the fact that there is no jacket makes it less formal. Your dad should wear a suit. It doesn't have to match the groom color-wise but for a daytime wedding, lighter would be better - such as grey.

The guys will have a tan jacket to match, and my dad tux is less formal- it has a tie instead of bow-tie, etc.

No, it'll be a nice contrast, especially for the family photos. I wouldn't have him get something else just to match.

It's unnecenssary to spend extra money. Your father can wear what he have. When you stand together to take pictures, different color can ceate good contrast and strengthen the effect.

Your dad does not need to match the other men. Contrast is good and if your dad already has a black tux/suit no need for the extra expense.

My dad is also wearing black. FH and the groomsmen are wearing brown. I think but am not 100% sure about FH's dad and stepdad but I think they are wearing grey suits they already own.

My dad is also wearing black. FH and the groomsmen are wearing brown. I think but am not 100% sure about FH's dad and stepdad but I think they are wearing grey suits they already own.

It's up to your dad if he wants to match. I think it's nice when the father's look similar but not matching exactly.

My FH and the groomsmen will be wearing black tuxes, and so is my dad, but then they are wearing different coloured ties (red for FH, blue for GM, and my dad said he would wear a different colour, gold perhaps?)

If you dad would rather wear something he already has, that's fine too.

All of the men in our wedding are wearing charcoal gray tuxes, but FH has ivory accents, GM have plum accents, and Dad has champagne accents.

I don't think he needs to match. For our wedding, FH and the groomsmen will all be wearing gray, but FH will be in a shade lighter than theirs. Both of the dads are wearing black.

No.

My FH is wearing a blue suit and my dad will have black.

I think it looks nice if the Dad coordinates with the wedding party but I like everything to look matchy. Our groomsmen are going to be in grey vests, the groom in grey suit and I am thinking my dad can be in a different shade of grey or black. The most important thing is that you keep the level of dress the same (formal or informal).

My FH and his groomsmen are wearing a lighter gray tuxes and our dads are wearing a darker gray.

Dads will generally wear the same tux just different vest/tie combination. You want to distinguished him from a groomsmen. Think of it this way - if a random person saw a picture of your wedding they could tell he wasn't just a groomsmen, but your dad