"Clean" tone is a relative term, especially when talking about tubes.
Nearly all amplification circuits introduce artifacts into the waveform; what you put in is not 100% exactly the same as what you get out. Most solid-state circuitry can achieve a waveform that is 99.5% "similar" or better; that is, they achieve less than .5% total harmonic distortion or THD. Some can achieve <.01%. This is, in the technical sense, a "clean tone", where output == more input, and this is generally preferable for most professional audio amplification needs. However, it can result in a disagreeable tone for an electric guitar (and other instruments); too much highs, too much mids, too "angular" a tone, etc.
Tube amps have a markedly higher THD; the circuit doesn't respond to the waveform as fast, and the ratio of peak input to peak output in the waveform diminishes earlier, but more gradually, than solid-state. In layman's terms, tubes "distort" the wave more than solid state at all signal levels, "coloring" the tone of the instrument, and they "clip" at lower levels than SS. But, tubes have a softer "peak" level than SS circuitry. which will simply "chop off" the waveform at the maximum gain level. Tubes instead "squish" the parts of the wave that exceed the max gain.
So, your answer is, at low signal levels that both circuit types can produce without clipping, there will be a slightly different tone produced by the tube amp, but unless you are comparing two amps side by side you would not detect the difference (and amps of all types will produce tonal variances regardless of tubes vs SS). At higher signal levels, the SS amp will still have "headroom" while the tube amp starts to "squish" the waveform peaks. In this grey area between clean and overdriven tone, you'll get a lot of different behaviors between SS and tube and between various circuit designs. Obviously, at "true" clipping levels, SS will produce a markedly different waveform than tube and the difference is quite noticeable until you push both amps into an extremely square wave.