IMO it's impossible to diagnose a the end of a computer line.

My advice is get to a proper bike fitter and get a "dynamic fitting" done - i.e. one where they not only measure your body and joint mobility, but put you on a fitting bike, wire you up with the led markers, and put you through a session where they video your joint movement in real-time, whilst riding (basically a full Retul (other types may be available, but that's the one I had, so I can give a few details of it) fit and "ride gait analysis") - this will determine if you're heel is throwing in/out at varying angles during the pedal stroke, and if you need differing cleats - I ride with Shimano SPD-SL's myself, and ended up with being recommended the yellows on my left leg, and the blue on my right - though to be honest at the moment i'm running yellows both sides...

Was a VERY extensive procedure, and in my case ended up with 3 visits in total, over the space of 8 months, punctuated by 6 months of physio and gradual alteration of my whole position on the bike - but then it was addressing a substantial difference in leg length after a large accident, and most of the physio was actually towards sorting out the lower back and hip issues that the leg length discrepancy had caused. Then the second visit began to actually work on addressing the imbalance in power between the two legs, and again my position (and cleat setup, shoe setup, orthotics, saddle height and bar reach ) was tweaked over a further couple of months. Finally, a third visit confirmed the eventual setup, and I got the figures I needed to actually start looking for my "dream bike" at the time - which has pretty much had a static setup for the past 3 years or more.

Not a cheap, or quick process, probably the cost of a good set of race alloy wheels just in Retul fees... Overall (when you figure in the Orthotics, cleats, swapping pedal systems on 2 bikes, swapping chainsets for different length crank arms, stems, bars etc.), probably nearer to the price of a pretty posh powermeter. But it's made a FAR bigger improvement to my cycling performance (not necessarily speed, I'm not a racer anymore - not since the accident that caused the leg length issue) and ability to enjoy time/distance in the saddle... Before this, if I rode for more than 2 hours, the following morning I'd often be crawling to the loo rather than walking... By the end of 9 months (admittedly, 9 months of generally pretty miserable times and lots of exercises and pain) I was able to ride 7-8 hours and be functioning perfectly well the following day, or to ride back to back 100km+ rides.

If you don't fancy the whole process, or think it's too much money, then stick with the yellow cleats - there's a reason that they're the "default" issue cleats - you're much less likely to do damage to your knees etc. by a miss-aligned cleat with +-6 degrees of float, than with one that has only +-3 or Zero float. I really do consider the blue and red cleats just as items that are there to address a problem that's been properly diagnosed - and that brings me back to my opening sentence...

it's excellent...

the "fitting bike" was basically built onto a computer controlled resistance unit (in the case of the one i used, it was a Tacx, pretty sure it was the "engine" from either the Genius or the Bushido - and they ran the Tacx TTS software to perform "ramp tests" while filming with a video and IR scanner (the led tracers were actually IR leds) from the front and the side. the video from each camera was then "overlayed" with a "stick trace" of where the IR leds were in 3 dimensions - so you could see (for example) how your knees tracked side to side during the entire pedal stroke - or if you dropped your heels more if you were pedalling slower cadence than higher... Then, you pedal at a fixed cadence and resistance, and they can raise/lower/fore/aft the saddle (it's on a winder crank) and see how it alters the tracking. Same with the 'bars - looking for shoulders rolling, and also how different shoulder positions stabilise/destabilise the hips...

it's one hell of a machine...



but the clever stuff really is with the video analysis, allowing you to slow down the movement, or just visualise it as a "stick man" diagram... really shows any imperfections in the pedalling action - in my case, because one leg was shorter than the other, I'd tried to lower my saddle to stop over-reaching with that leg, or "rolling over the saddle" and getting sores on the undercarriage... This resulted in my longer leg's knee "throwing outward" at the top of the stroke, which in turn caused a twist in my hips, flexed the back muscles on that side only, AND ended up causing pain in the knee itself and the ankle... So, we basically raised the saddle again, moved it slightly backwards, shortened the cranks marginally and used a combination of sub-cleat shims and eventually an Orthotic in the short-leg shoe to redress these problems. The Blue cleat was also fitted on the LONG leg side, to help to control my baked-in (from years of riding with the saddle too low) tendency to throw the knee... Actually, the cleat was set "crooked" on the foot, which basically instead of +-3 degrees effectively gave +6,-0 degrees of float - i.e. I could twist my heel outward as much as I was used to, but NOT inward (as that was one of the ways to prevent the knee throwing outwards...)

As I said, was a long slow process for me, mainly because I tried to fix the problem maybe 15 years after the accident that caused it, and after 5 years of cycling (I didn't dare ride for the first 10 years after the accident...) that'd ingrained the bad habits / problems.