Steering Shake but not always - Will Castor Correction Bushes fix the problem?

Dear all,
I've been reading pretty much about all the info about the correction bushes, and I've got a question.

My 2010 Jimny has a 2'' lift kit from Jimnybits. I've been driving it with the stock wheels and tires all summer, and now I have installed 31''x10.5R15 tires and rims. 

Needless to say, I knew that the steering would be altered, for example it does not return itself on turns. However, sometimes (and not always) the steering becomes shaky on straight lines and top speed. 

Will the Old Man Emu castor correction bushes from Jimny bits fix also this issue? If so, I noticed there are 3x different colours for sell on Jimnybits, the yellow, red and purple. Is it just a material difference? 

If so, can anyone with experience on this product, advise which one to get, and if it will fix my shaky steering on straight lines?

Thanks a lot!

I would have thought that Jimny-Bits are the people to ask.

Roger

You've fitted larger wheels and now you have a "shimmy" at speed - the most likely cause is out of balance wheels.

The "not returning to center" is most likely caused by incorrect caster angle, which can result from a lift, and caster correction bushings can be used to fix this, but I would suggest that you have the caster checked to see what it is before proceeding.

I would not expect caster correction bushes to fix an out of balance wheel problem, but insufficient caster angle can contribute to the shimmy.

You say top speed are we talking 85+ mph
Have you changed track rod ends all 4
When did you last change kingpin bearings 
Castor bushes will only help steering self centering 
Have you fitted new branded tyres or retreads? 
I have 32's fitted and use dyna beads for balancing