The event started while on a return leg from KTUL to KSWO. I was in a Cessna 150 at approximately 3,000ft MSL HDG 270T. Approximate local time was 2000 at the start of the sighting. Visibility was significantly greater than 10 Statute Miles. Temperature was approximately 85F and wind was around 3KTSOn my return leg back to KSWO from KTUL at Approximately 2000, I was following Highway 51 about 20nm to the East of KSWO when I noticed a very bright light BRG045. Approximate location of my aircraft at time of sighting was N36 06.78 W096 44.52. Approximate location of object at time of sighting was N36 24.66 W096 58.62. I initially noticed the object during my routine scan outside the aircraft for aircraft operating in the local area. KSWO was my home airport, and is also the location of a University flight school. The light's appearance was a brilliant white, like a large aircraft's landing light. My initial reaction was that it must be either a planet, or more likely a large aircraft in the pattern at KSWO. As the sighting progressed, I began to dismiss the previous objects as it was too far below the horizon to be an astronomical object, and lacked recognition lighting that is common to all general aviation and commercial aircraft. During the initial part of the sighting, the object exhibited CBDR or Constant Bearing, Decreasing Range; it was heading towards my aircraft. This lasted for 15 minutes. Estimated airspeed of the object at this point estimated to be less than 50KTS. As I begin to descend into KSWO at 2015, I started talking with another pilot in the vicinity of the airfield operating a powered parachute. At this point my attention went from the unidentified light, to descent and pre-landing checklists and I lost sight of the object. Upon landing at the airfield at 2025, I notified the operator of the powered parachute that I would be interested in coming to look at his aircraft after I had secured mine for the evening. He accepted my offer, and I parked my aircraft and secured it for the evening.At 2115 I drove to a nearby hanger on field at KSWO to meet the operator of the powered parachute. When I arrived, he along with a friend and his son were on site. They were looking at an object through a pair of binoculars that was now directly south of our position. The 3 individuals explained that they had witnessed the object transit from above Ponca City, OK....pass Stillwater, OK (KSWO)....and was not observing the object (along with myself) in the vicinity of Oklahoma City, OK. Witnesses described the object as I had in my description earlier, and that it produced no audible noise. At 2120, I obtained the binoculars and looked at and re-acquired what I assess was the same object that I had sighted earlier. Approximate location of the object was now N35 40.08 W097 21.96 which was directly south and slightly west of my position which was still KSWO. While looking through the binoculars I could determine the object was spherical in nature and estimated its size to be about 30ft in diameter. With the naked eye from my viewing location, it appeared to be about half the size of an aspirin held at arm's length. Through the binoculars I could clearly see the object "morph" through a color pattern. This patter was similar to the lighting that you can commonly find in limousines and other entertainment events. I would describe it as "party lighting". The sphere emitted an aura of light in a cyclical manner that was predominantly Red/Orange and Green/Blue. I observed the object in this location for approximately 20 minutes until approximately 2140. During this period of observation, the object remained stationary. At approximately 2140, the object slowly "winked out" and became invisible to the naked eye as well as through binoculars. I feel that I was very calm and objective through the entire encounter. I am an expert in identifying aircraft of all types under all conditions. I was and still am unable to identify the craft/object that I witnessed. Although I feel that this aircraft could be attributed to a terrestrial craft/event, I feel that this is unlikely after my observations.I am attaching a Powerpoint/PDF document illustrating my encounter. Additionally, I am attaching a photo I found on the internet which most closely depicts the object that I observed.