will we ever see a simian spirit guide style card in black, blue, or white? if not will ever see a another SSG in R or G?

It’s not an ability that particular fits white orblue’s color pie. Maybe black if it’s accompanied by life loss.

Hi Mark, I'm a big fan of Simian Spirit Guide and Elvish Spirit Guide. Will cards like this be made for the other colors as well, or will this be a Yavimaya/Urborg where only certain colors get it?

It was never intended to be a cycle.

Could Black get a color shifted Elvish/Simian Spirit Guide if there was some sort of life payment?

It can do it in color pie, but play design might not want to make it.

With regards to Simian Spirit Guide, the card it’s a riff of, Elvish Spirit Guide, was from Alliances. Alliances had a heavy Ape theme in red, so it’s an Ape because if it had originally been printed in Alliances, that the type it probably would have been.

Good point.

Is simian spirit guide more in colour than elvish spirit guide?

The ability is now red. Whether or not it’s something anyone should have play design-wise is up for debate.

What color would you say currently has the "spirit guide effect?" It seems to work for either red or green, but Simian Spirit Guide has a colorshifted border...

It’s probably Red… If it’s an effect developmentally we want to do.

Thanks to Planar Chaos, there are a number of effects that exist in Modern in the "wrong color," while the right-color version has never been reprinted. Two examples off the top of my head are Simian Spirit Guide/Elvish Spirit Guide (arguably) and Mana Tithe/Force Spike. Do these color pie violations bother you more than others? (They do me.)

Planar Chaos stretched the color pie but not to the point of undercutting the weakness of colors, so those don’t bother me nearly as much as cards that let color’s do things that by color definition they aren’t supposed to be able to do.